Post by: PJM47 on August 30, 2020, 09:22:42 AM
I have a CB750K2 which was running fine, I haven't used for a few weeks and when I went to start it yesterday it turned over very slowly then the engine just locked up completely. It is now stuck solid, kickstart or rear wheel in gear won't move it. On investigation i discovered to my horror that I had what seemed like an entire tank of fuel inside the engine! I left the fuel tap on and somehow the carbs leaked into the engine and gearbox rather than come out the overflow. I have drained all the fuel and removed the plugs but the engine is still stock solid. Any ideas of what the damage might be? Is there any thing I can check to narrow it down, not sure I am up to a complete engine removal and strip down?
Post by: Johnwebley on August 30, 2020, 09:27:13 AM
Try to turn it in reverse.
See what happens
Sent from my SM-A750FN using Tapatalk
Post by: PJM47 on August 30, 2020, 09:36:08 AM
Post by: PJM47 on August 30, 2020, 09:48:37 AM
Post by: K2-K6 on August 30, 2020, 09:54:47 AM
Not a nice prospect, but a very real possibility. Difficult to assess though without some level of dismantling, if it's not turning with the fuel drained from it then obviously some mechanical change could have taken place.
Post by: K2-K6 on August 30, 2020, 09:56:05 AM
Post by: Nurse Julie on August 30, 2020, 09:57:36 AM
Post by: Bryanj on August 30, 2020, 10:12:18 AM
Post by: ka-ja on August 30, 2020, 10:22:04 AM
Post by: Bryanj on August 30, 2020, 11:57:06 AM
Post by: Lobo on August 30, 2020, 11:59:06 AM
Is it possible, that fuel has pooled in the sump below the pistons and locking from below... ie have you taken the sump plug out / oil filter off to drain all fluids as the next step?
Post by: Johnny4428 on August 30, 2020, 12:12:08 PM
Post by: PJM47 on August 30, 2020, 12:14:51 PM
Post by: McCabe-Thiele (Ted) on August 30, 2020, 12:41:10 PM
When you removed the oil filler cap did flud run out then?
Not sure from your description if you cranked the engine with the electric start or with the kickstart it needs a fair bit of pressure to bend a con rod.
I've seen flood damaged engines on Petrol & Diesel engines from when I worked at local MB dealership for 11 years - they tend to bend and often snap con rods or push them through the block as well as piston & valve damage. That said the damage was done when the engine was running. i would expect your damage to be more limited as it was done when attempting to start the engine so less force in play.
Post by: Bryanj on August 30, 2020, 01:27:35 PM
Post by: K2-K6 on August 30, 2020, 03:50:56 PM
Detecting accurately without internal inspection may be difficult, at least I can't immediately think of a competent way :)
It takes only a small amount of fluid (anything much above tdc combustion chamber volumes) to compromise a rod. It's even more effective with less total volume error above chamber volume as the crank can build more approach speed until it meets resistance, and finally tweak the rod as it won't go over compression.
Vaguely better news ( again, if this is the cause) is that it may be only one piston as it's pair cylinder would have valves open at the same point. If that's the case, then damage may be very minor with just one piston cocked side ways and locking the crank.
Post by: Lobo on August 30, 2020, 10:53:06 PM
That’s said perhaps a waste of time as this does sound to be a head off. Feeling bad for you PJM47..., and kinda wondering why we don’t hear more of such failures given the number of CBs out there...
Post by: MrDavo on August 31, 2020, 11:18:35 AM
My wife, acting as designated driver on the way home from a bike club ‘do’, once drowned my 2.8 V6 Capri, by driving it through a flood. The air intake was quite low down, next to the headlights behind the front grille. We got out, getting us and the interior very wet, and pushed it to safety, then idiot here decided to try and bump start the car. No joy, it wouldn’t turn over, and the next day when I took the plugs out, jets of water shot out of the plug holes as I cranked the engine.
I got it running again, but with a loud death rattle, which turned out to be displaced main bearing shells if I remember correctly. I do know I had to pay a shedload of money to have it fixed.
Post by: PJM47 on August 31, 2020, 11:29:03 AM
Post by: Bryanj on August 31, 2020, 12:13:18 PM
Post by: rosco on August 31, 2020, 05:02:07 PM
Post by: royhall on August 31, 2020, 05:39:48 PM
Post by: Bryanj on August 31, 2020, 05:47:00 PM
If you try you will wreck the advance unit. If you want to try turning the crank remove the generator cover and try on the big bolt holding the alternator rotor
Post by: royhall on August 31, 2020, 05:59:37 PM
Post by: PJM47 on August 31, 2020, 06:58:45 PM
Post by: K2-K6 on August 31, 2020, 07:35:33 PM
Have you thought it could be the gearbox stuck??? My brother bought a cb550 with a "seized engine " Turned out something in the gearbox let loose [ can't remember what ] and jammed the gears and broke a few teeth Try pulling in the clutch and using the kickstart If the kickstart don't move its the gearbox If it does move more than likely engine Good luck R
It doesn't turn on the starter either I thought.
Kickstart essentially bypasses the gearbox on these by just going down through the primary chain to the crankshaft, hence you can pull the clutch and start it whether it's in gear or not.
Post by: Bryanj on August 31, 2020, 11:36:32 PM
It is only permissible to use that big nut with plugs out on a free turnung engine and its not really advised even then
Post by: royhall on September 01, 2020, 07:14:48 AM
I should make it clear now that I used the words gently and very gently and only millimetre movements. It was not my intention to use the timing end it break the engine free with a scaffold pole, just to establish which part of the engine is locked.
It may be wise to establish the facts here. Firstly what level of mechanical competence does PJM47 have, I assume as he's talking about repair engineers he's not a professional. Are you a competent DIY mechanic or a complete novice or somewhere in between. Was the bike left on the side or main stands? On the main stand the leak would fill the airbox first as the intake side is slightly lower (on the F2 anyway). If it cannot escape from the airbox as the petrol level rose it would then fill all 4 cylinders via the airbox. The cylinder with two closed valves would hold fuel in the intake so when the engine turns that fuel gets drawn into the cylinder and before it can leak down past the rings the engine comes back to compression and bends a rod or tips a piston jamming it into the bore.
Also, just how much petrol are we talking about here, you appear to say it could be around 2 to 3 gallons sat in there over a good few weeks? With the limited space inside a CB750 engine that is enough to fill the thing from top to bottom. If that is the case, a complete strip and rebuild is the only way forwards. The fuel will be in all the bearings, oil pump, oil galleries, alternator, clutch, scavenge lines, oil filter etc etc. Even if you can achieve turning the engine again it would require careful work to safely run it again. If there's fuel in the oil galleries clean oil would need to be slowly pumped through the engine to re-lubricate everything with the sump plug out to drain the fuel pushed through. You would need to remove the scavenge line to the oil tank to prevent fuel contaminating the oil in the tank. And don't forget were also talking Ethanol here that loves to remove lubricating oil.
In my view this engine needs stripping to clean everything out and re-lubricate everything and locate the damage. The alternator needs cleaning and drying off and testing. I many years ago foolishly cleaned some clutch plates off a Suzuki in petrol and the corks grew to about twice the thickness they should be which cost me a clutch, so that will need checking. Then lets not forget the failure in the carbs that allowed this to happen that also needs sorting, plus the airbox will be full of fuel.
If it were me I would take out the clutch plates to disconnect the engine from the gearbox physically then put the bike in gear and gently turn the back wheel and see if the clutch inner turns. That verifies the gearbox is not locked and it's therefore in the engine/kickstart mechanism. At that point see if the engine turns (please do this very gently). But that only establishes the area the damage lies and the engine will need stripping anyway.
Sorry to be the bearer of bad news and I do sympathise whole heartedly with you. But if the bike was mine I would bite the bullet and get the engine out. It's a big price to pay for forgetting to turn off the fuel tap, and not one of us on here can say we have never done that, we just got away with it.
Post by: PJM47 on September 01, 2020, 06:03:17 PM
I’m a fairly competent diy mechanic and will tackle most jobs but obviously this is pretty major and might be best left to a professional, ouch!
Post by: rosco on September 01, 2020, 06:19:48 PM
Post by: K2-K6 on September 01, 2020, 06:26:20 PM
Some oil will drain out but not much, just residual.
Also in the interests of investigative examinations, could be worth removing the float bowls and trying to gently blow, mouth? Not compressor, down the overflow tube to see if any are blocked which would cause the fuel to exit via jets into carb throat. It may illuminate which cylinder the fuel was routed through.
Which area of Hampshire are you located?
Post by: rosco on September 01, 2020, 06:52:50 PM
Post by: PJM47 on September 01, 2020, 07:31:32 PM
Post by: K2-K6 on September 01, 2020, 07:35:19 PM
Have you tried to turn it over in each gear to eliminate the box If all ok and engine won't turn on either kick start or button likely to be engine locked up Agree with Roy best to take engine out to investigate First check cam chain ok
The kickstart engages a gear directly on the clutch basket, which in turn is directly connected via spline drive to the primary chain coming from the crankshaft. By removing the clutch plates the gear ratios have no connection at all with the engine / crankshaft assembly.
The OP should be able to turn the centre shaft of the clutch (rotaing the gearbox) and demonstrating it's free, but not the clutch outer basket as it's still directly connect to crankshaft.
Post by: PJM47 on September 02, 2020, 12:40:10 PM
Post by: K2-K6 on September 02, 2020, 04:58:59 PM
Oh! with a scope you can also look at the cam chain at the top through #3 inlet tappet cover to make sure it's not snapped. That's a pretty remote half chance and highly unusual but very remote possibility and worth a look-see.
Post by: PJM47 on October 05, 2020, 05:20:52 PM
Post by: Nurse Julie on October 05, 2020, 05:30:03 PM
Post by: Trigger on October 05, 2020, 05:32:17 PM
Post by: JonnyB on October 05, 2020, 05:46:48 PM
If not remove the clutch or just the plates. if it still won't turn over it's engine. if it does it's clutch or gear box.
I've not read the whole post. have you drained the sump since? I've had this issue on a GS450. it locks the top and bottom and the clutch plates can bind.
Sent from my SM-G935F using Tapatalk
Post by: royhall on October 05, 2020, 05:59:53 PM
I'm with trigger. you need to ascertain if the engine will turn over. Normally with it in neutral the engine will turn over easily with a spanner on the crankshaft end.That's all been covered earlier in the thread.
If not remove the clutch or just the plates. if it still won't turn over it's engine. if it does it's clutch or gear box.
I've not read the whole post. have you drained the sump since? I've had this issue on a GS450. it locks the top and bottom and the clutch plates can bind.
Sent from my SM-G935F using Tapatalk
Post by: PJM47 on October 05, 2020, 06:30:14 PM
Post by: Trigger on October 05, 2020, 06:47:53 PM
Check the teeth on the clutch basket and check the teeth on the kick start wheel. Also make sure the kick start cog/ wheel is running true as in not bent.
If everything looks good then put the basket back in and try to kick it in neutral.
Post by: PJM47 on October 05, 2020, 07:01:25 PM
Post by: PJM47 on October 06, 2020, 07:56:04 AM
Post by: Trigger on October 06, 2020, 08:22:31 AM
Post by: PJM47 on October 06, 2020, 10:57:29 AM
Post by: Trigger on October 06, 2020, 12:19:23 PM
Now without the basket in can, you turn the shaft easy and select all gears that way ?
Do you have the transmission cover off ? I would like to see a picture with that cover off.
Post by: PJM47 on October 06, 2020, 01:58:56 PM
[attachimg=1]
Post by: Trigger on October 06, 2020, 02:11:48 PM
Now, this is not making any sense. The kick start cog turns the clutch basket with is on the shaft. If the kick start is working fine and it sounds like it is, then the kick should turn the basket which, turns the shaft.
Post by: K2-K6 on October 06, 2020, 02:19:41 PM
Yes anti clockwise, it actually turns both ways. will check things you suggest and and try the basket back on tomorrow.
Could be that the starter sprag clutch was jammed so trying to turn the starter motor (from mechanical means) all the time.
Could try removing the starter motor and see what you get.
As Graham says, it's not adding up so something we're missing somewhere.
Post by: PJM47 on October 06, 2020, 02:24:44 PM
I'll have a look a the starter next. Is it easy enough to remove?
Post by: Trigger on October 06, 2020, 02:29:21 PM
[attachimg=1]
Post by: Trigger on October 06, 2020, 02:38:44 PM
Yes anti clockwise, it actually turns both ways. will check things you suggest and and try the basket back on tomorrow.
Could be that the starter sprag clutch was jammed so trying to turn the starter motor (from mechanical means) all the time.
Could try removing the starter motor and see what you get.
As Graham says, it's not adding up so something we're missing somewhere.
If the alternator housing is off, all you need to do is remove the small cog that connects the flywheel to the starter motor so, no need to remove the starter ;)
Post by: Primus on October 06, 2020, 02:58:10 PM
Paul
Post by: K2-K6 on October 06, 2020, 03:01:57 PM
Yes anti clockwise, it actually turns both ways. will check things you suggest and and try the basket back on tomorrow.
Could be that the starter sprag clutch was jammed so trying to turn the starter motor (from mechanical means) all the time.
Could try removing the starter motor and see what you get.
As Graham says, it's not adding up so something we're missing somewhere.
If the alternator housing is off, all you need to do is remove the small cog that connects the flywheel to the starter motor so, no need to remove the starter ;)
Ooops, I forgot the alt cover was off :)
Also then, can check the sprag clutch by rotating the big gear, should try to turn turn the crankshaft if pushed anti clock, and spin freely if you rotate clockwise.
Post by: royhall on October 06, 2020, 03:21:51 PM
Post by: PJM47 on October 06, 2020, 03:40:21 PM
I also removed the cog that connects to the starter motor and this made no difference.
Post by: K2-K6 on October 06, 2020, 03:43:54 PM
Post by: K2-K6 on October 06, 2020, 03:47:46 PM
Don't forget when the basket is out all turns well so not going to be starter or sprag clutch. My money's on the part that trigger posted a picture of, something has seized in that. That's the union piece between the two halves of the engine. This is like a whodunnit murder mystery.
I was thinking the same Roy, but with all assembled AND in neutral, then the whole lot can go round unimpeded. Very puzzling.
Post by: PJM47 on October 06, 2020, 04:07:39 PM
Post by: Trigger on October 06, 2020, 05:01:20 PM
I would say, pop the engine out and throw it in the car and bring it to my workshop but, it is not that easy to just pop a CB750 SOHC engine out.
Post by: K2-K6 on October 06, 2020, 05:23:37 PM
See if you've any "spare parts" lying in there.
Oddly I was in your area 3 weeks ago to collect a tent I bought on the bay of E, and was followed by an F2 along the old A3.
If you can't take up Trigger's offer I could come down to have a look with you at some point.
Post by: McCabe-Thiele (Ted) on October 06, 2020, 05:34:27 PM
Post by: MrDavo on October 06, 2020, 06:03:52 PM
No idea what, but given the circumstances in which it happened, my money is on something, maybe in the gearbox, being bent, which isn't going to unbend itself. Maybe it wants to be in an 'impossible' gear.
Unfortunately the only way to find out what, and fix it, is to dismantle. When my crank went up the pictures I got my engine out in an afternoon (with help with the lifting), you can then turn it upside down and split the cases without touching the top end, if I remember right. If not someone will be along soon to call me an idiot.
Then K2-K6 will tell me how long Honda allowed for an engine removal....
Post by: K2-K6 on October 06, 2020, 06:59:40 PM
Lifted many of them out though, in a more relaxed fashion :) usually trying to be real careful not to scratch anything.
Post by: PJM47 on October 06, 2020, 07:13:06 PM
Post by: Trigger on October 06, 2020, 07:22:29 PM
:) "Then K2-K6 will tell me how long Honda allowed for an engine removal...." I'm not from official workshops so haven't a clue :D Bryan and Ken usually know that in more detail.
Lifted many of them out though, in a more relaxed fashion :) usually trying to be real careful not to scratch anything.
I can't remember what the book says on hours for a engine removal on a 750 but, i had a customer that had a quote for £665 engine removal on a 750 then the same again to get it back in plus £45 a week storage charge for the rolling chassis until i rebuilt his engine and then £225 set up fee including tuning :o
Post by: K2-K6 on October 06, 2020, 07:27:01 PM
Post by: Trigger on October 06, 2020, 07:29:43 PM
Post by: MrDavo on October 06, 2020, 08:26:12 PM
Post by: royhall on October 06, 2020, 09:02:22 PM
Post by: SumpMagnet on October 06, 2020, 09:12:29 PM
Having shifterd a KAwasaki 750 motor on my own before...I was unprepared for just how damn heavy the 750-4 engine is
Post by: Trigger on October 06, 2020, 09:27:34 PM
I think that's a classic case of pricing yourself out of the job because he didn't want to do it.
Nope, as i asked about and that is a standard rate these days at a main dealer. They would have to carefully store the exhausts, tank, side panels and the rest of the bike. Then not damage the bike frame in any way or the customer could claim.
Post by: royhall on October 06, 2020, 10:21:01 PM
Post by: Trigger on October 06, 2020, 11:23:01 PM
Post by: Bryanj on October 07, 2020, 12:59:24 AM
Post by: royhall on October 07, 2020, 04:52:13 AM
Post by: Bryanj on October 07, 2020, 07:41:45 AM
Post by: royhall on October 07, 2020, 07:43:17 AM
Post by: paul G on October 07, 2020, 07:45:55 AM
Just nuts, bolts and a hernia plus 2 boxes of elastoplastPlus a week of work with a bad back :o :o
Love the 400/4 engine as it can be done in the frame ;D ;D
Post by: JezzaPeach on October 07, 2020, 07:46:59 AM
Post by: flatfour on October 07, 2020, 08:47:06 AM
Post by: Trigger on October 07, 2020, 10:54:47 AM
Just nuts, bolts and a hernia plus 2 boxes of elastoplast
Not just nuts and bolts Bryan. Lost count of how many frame bolts i have had to oxy out.
We used to charge £85 to fit a exchange engine in the 90's and some customers thought that was too expensive and decided to take the engine out themselves. Had a few customers that had dropped there engine off a trolley jack while trying to save money. Even had one macho man who, instead of coming into the workshop and asking for help to get this engine out of his car, decided that it was a good idea to take it out himself, dropped it, then fell over it and broke his nose when he hit the floor :o
Post by: royhall on October 07, 2020, 11:08:25 AM
Priceless.Just nuts, bolts and a hernia plus 2 boxes of elastoplast
Not just nuts and bolts Bryan. Lost count of how many frame bolts i have had to oxy out.
We used to charge £85 to fit a exchange engine in the 90's and some customers thought that was too expensive and decided to take the engine out themselves. Had a few customers that had dropped there engine off a trolley jack while trying to save money. Even had one macho man who, instead of coming into the workshop and asking for help to get this engine out of his car, decided that it was a good idea to take it out himself, dropped it, then fell over it and broke his nose when he hit the floor :o
Post by: Bryanj on October 07, 2020, 02:02:56 PM
We found that it was easier for just one, strong, person to lift from box to frame and then the "helper" to get involved from other side of bike, this was when we were allyounger, healthier, fitter? and of course a damn site stupider
Post by: 71 V12 on October 07, 2020, 05:37:43 PM
https://youtu.be/Ezl3B5Jv6B8
Post by: PJM47 on October 07, 2020, 05:49:48 PM
[attachimg=1]
Post by: Nurse Julie on October 07, 2020, 05:53:48 PM
Post by: PJM47 on October 07, 2020, 06:20:46 PM
Post by: Trigger on October 07, 2020, 06:28:38 PM
Post by: PJM47 on October 07, 2020, 06:36:17 PM
Post by: K2-K6 on October 07, 2020, 06:40:42 PM
Probably that petrol wash it had!
;D ;D
Post by: Trigger on October 07, 2020, 07:21:42 PM
Post by: SteveW on October 07, 2020, 09:48:54 PM
Almost as good as when I was a kid eagerly waiting to find out who shot JR in Dallas.
Post by: Nurse Julie on October 07, 2020, 10:01:34 PM
This is one of the best threads ever.🤣 🤣 🤣 🤣 🤣
Almost as good as when I was a kid eagerly waiting to find out who shot JR in Dallas.
It's sort of like a murder mystery, I'm really enjoying it as well.
Post by: Laverda Dave on October 07, 2020, 11:12:29 PM
Post by: philward on October 08, 2020, 01:42:44 PM
Sent from my moto g(7) power using Tapatalk
Post by: PJM47 on October 08, 2020, 06:36:49 PM
I have everything stripped now ready for engine removal so hopefully won't be too long before the next instalment..
Post by: Trigger on October 08, 2020, 06:52:38 PM
Post by: Lobo on October 08, 2020, 11:28:44 PM
Post by: PJM47 on October 10, 2020, 02:50:24 PM
I have split the cases and everything looks ok. There wasn't a drop of oil anywhere though, everything had been washed clean by the petrol, so I oiled everything up I could and the engine started to turn over much easier on the crank, the more I turned it the better it got. I am now able to turn it a bit on on the kick starter, there is no way I could do this before. I'm not sure there was ever anything much wrong with the bottom end, could it be it was all just a bit seized up?
Do we think the issue was just that the pistons had seized up a bit after sitting in petrol for weeks and no oil and were reluctant to move, this might be consistent with the start of this thread where a few weeks ago I'm sure I couldn't turn it on the crank at all. Then when I tried again the crank would turn but it was still too stiff for the kick starter. Then finally after taking apart and oiling it is now free enough to move on the kickstart (a bit). It does seems to be gradually freeing up which would explain why the symptoms are changing and not making sense.
So what next? how easy should it be to turn the engine over (no plugs and lower case removed) on the crank, it's still seems a bit stiff and has tight and loose spots? But after a lot of turns I can now turn it a bit on the alternator just by hand, not all the way round though that steel needs a wrench. Is that normal?
What can I check to get a good feeling it is safe to put back together and try to start it?
And finally anything I should replace/check whilst its apart?
Post by: Nurse Julie on October 10, 2020, 03:03:34 PM
[attachimg=1]
Post by: K2-K6 on October 10, 2020, 03:35:32 PM
I've still a suspicion it's tweaked a rod from hydraulic compression, can you equate the tight spot to a regular positioning of one pair of con rods?
It should rotate with very similar friction for whole rotations just by hand on the alternator.
Pretty simple to work on though, aren't they?
Post by: Trigger on October 10, 2020, 04:25:46 PM
Can't see anything in the bottom end. Are all the cog teeth OK, no chips ?
Post by: PJM47 on October 10, 2020, 04:41:15 PM
What's this circled in red? (It could be something or nothing, difficult to tell on my phone)
Just a bit oil, cleaned off and there's nothing there.
Post by: PJM47 on October 10, 2020, 04:48:30 PM
The conrods don't look obviously bent but I guess it would be difficult to tell.
It is tighter when pistons 2&3 are down (compressed) and fairly loose when they are the way out.
So can I get to the pistons / conrods without opening the top end or is it now major strip down?
[attach=1]
[attach=1]
Post by: PJM47 on October 10, 2020, 04:49:59 PM
Post by: Johnwebley on October 10, 2020, 04:55:56 PM
Or the cam off?
If not. That may be the reason it is difficult to rotate.
The cam opening the valves
Sent from my SM-A750FN using Tapatalk
Post by: K2-K6 on October 10, 2020, 05:04:33 PM
You dont have to disturb the barrels and head at this stage.
Post by: PJM47 on October 10, 2020, 05:43:25 PM
Is there any fairly non intrusive checks I can do? Would it be silly to put it back in the bike now?
Post by: Nurse Julie on October 10, 2020, 05:54:51 PM
Post by: PJM47 on October 10, 2020, 06:12:39 PM
Post by: philward on October 10, 2020, 06:56:09 PM
Post by: Bryanj on October 10, 2020, 07:19:12 PM
Post by: SteveW on October 10, 2020, 07:21:36 PM
So if only a part of the cam is turning you could get more than one compression stroke at a time and therefore way more difficult to turn engine?
As I said I don't know if this is even possible but a mate of mine did have a cam shear in two in his car once.
Post by: Bryanj on October 10, 2020, 07:26:28 PM
Post by: K2-K6 on October 10, 2020, 07:31:25 PM
Post by: PJM47 on October 10, 2020, 07:57:54 PM
Post by: PJM47 on October 11, 2020, 09:33:16 AM
Cam out and head off next then. I'll read the manual, but any top tips I should be aware of?
[attach=1]
Post by: bobv7 on October 11, 2020, 09:40:09 AM
Post by: Johnwebley on October 11, 2020, 09:47:45 AM
It should be fairly easy to turn over.
Sent from my SM-A750FN using Tapatalk
Post by: Trigger on October 11, 2020, 09:56:16 AM
All looks ok under the rocker cover.
Cam out and head off next then. I'll read the manual, but any top tips I should be aware of?
(Attachment Link)
I see a lot of damage were people put the wrong length bolts in the wrong place when putting the cam towers back on. There are 4 bolts that have number 7 on the head, make sure these go back were you took them from as, they are a tad longer than the other bolts and if in the wrong place will punch the bottom of the thread holes out and will leak.
What you need to do is remove the rockers and get the cam chain off. Leaving the cam towers on the head, place the cam shaft back in the towers and put the cam caps back on. Bolt it down and see if the cam rotates easy in the towers. This will rule out it the cam shaft is bent or not.
I still have not seen anything untowards from the pictures. Have you assembled the gear box in the lower casing and with the clutch basket on, tried the kick start ?
Post by: K2-K6 on October 11, 2020, 01:01:26 PM
It obviously won't check the cam as trigger has indicated above though.
Post by: PJM47 on October 11, 2020, 04:45:44 PM
This thread started in August and it's now October and not a lot seems to have changed. WTF???? ::)
I've only just started stripping it down last week as I've been busy with other projects.
Post by: PJM47 on October 11, 2020, 04:52:38 PM
Cam out, no change.
Still very stiff to move in places.
Everything looks ok with the cam though.
Head coming off next then.
[attach=1]
Post by: Trigger on October 11, 2020, 06:01:54 PM
OK so rockers off, no change.
Cam out, no change.
Still very stiff to move in places.
Everything looks ok with the cam though.
Head coming off next then.
(Attachment Link)
The cam chain is still on in your picture
Post by: PJM47 on October 11, 2020, 06:47:36 PM
Post by: Trigger on October 11, 2020, 07:14:29 PM
Post by: PJM47 on October 11, 2020, 07:25:31 PM
Post by: K2-K6 on October 11, 2020, 07:39:21 PM
You'd expect to find witness marks on the big end shells as they would effectively try to wear "diagonally " which if wearing away would slowly allow you to turn it as the shell material wears off. Potentially ;D
PJM47, notice, from dismantling, how you can set the cam timing with absolutely no risk when you come to reassemble as nothing interfears while rotating/ checking until you put the rockers in. It's a very clever design like that.
Post by: PJM47 on October 12, 2020, 06:24:30 PM
Indeed this engine is beautifully designed, unlike the British ones from the same era I've worked on.
Still very hard and uneven to turn over as we would expect. So I guess fairly conclusive big end / conrod damage now as there's not much else left.
[attach=1]
Post by: royhall on October 12, 2020, 06:27:21 PM
Post by: philward on October 12, 2020, 06:33:56 PM
Post by: PJM47 on October 12, 2020, 07:00:58 PM
Not necessarily, it may just be completely lacking in lubrication.
Ok sound like a plan, will do this next.
Post by: Trigger on October 12, 2020, 07:44:08 PM
Post by: PJM47 on October 12, 2020, 08:35:51 PM
Post by: PJM47 on October 13, 2020, 05:18:06 PM
So I removed one rod at a time as suggested thinking at some point it would free up, but got to the last one and guess what, it is still exactly the same, it turns a bit then gets stuck. As everything is loose it now actually lifts the crank out of the case / bearings if I try to turn it more. The primary chain is off at this point and there is nothing left connected just the crank sat in its slot, it won't rotate freely.
It looks like the big gear behind the alternator is right up against the case and maybe getting stuck in places, its very close anyway. So bent crank or maybe just that gear is bent? Should it be so close to the case?
[attach=1]
[attach=2]
Post by: royhall on October 13, 2020, 05:25:43 PM
Post by: PJM47 on October 13, 2020, 05:27:51 PM
Just try oiling the shells they won't turn bone dry.
Yes they are all fully oiled
Post by: Trigger on October 13, 2020, 05:29:38 PM
Post by: MrDavo on October 13, 2020, 07:03:11 PM
Quote
it now actually lifts the crank out of the case / bearings if I try to turn it more.
I'll take bent crank please Eamon. I've bent a Triumph T140 crank, and they are positively agricultural in comparison. Amazing what hydraulic lock can do, its the irresistible force meeting the immovable object, but something has to give.
Post by: K2-K6 on October 13, 2020, 07:07:39 PM
I'd not have guessed at that from the beginning. On the positive side, it shows how strong the rods and starter motor are :D
Post by: allankelly1 on October 13, 2020, 07:10:41 PM
Good luck
Best wishes Al
Sent from my iPhone using Tapatalk
Post by: royhall on October 13, 2020, 07:12:21 PM
Post by: Trigger on October 13, 2020, 07:39:11 PM
Post by: PJM47 on October 13, 2020, 08:31:07 PM
The wear on the shells is fairly even.
The flywheel gear is so close I can’t get my smallest feeler in between it and the case, that doesn’t sound right, and there are marks on the case where it looks to have rubbed.
Post by: MrDavo on October 13, 2020, 10:53:23 PM
Possibly the starter clutch arrangement is damaged or bent instead, that would be a far better outcome than the crank. I had a tool to get the alternator off but nothing would budge, I ended up going to a local engineering shop. Trigger’s yer man there, however if it is now on skewiff then things may not be straightforward.
Post by: K2-K6 on October 13, 2020, 11:10:32 PM
It may prevent the starter motor from operating, if it were damaged. But the kickstart doesn't go through that way, it's via the primary drive direct to crank and avoiding the starter gear.
You'd have imagined that the kick would still work in the above scenario.
Also if main bearings where dry, it's likely that it would be consistent in resistance for whole rotations, and not more pulse like.
Post by: McCabe-Thiele (Ted) on October 13, 2020, 11:33:47 PM
Is there any kind of spacer or thrust washer between the gaer and the crankcase any end float control?
Post by: Bryanj on October 14, 2020, 12:21:59 AM
Post by: McCabe-Thiele (Ted) on October 14, 2020, 10:15:03 AM
Post by: Trigger on October 14, 2020, 11:27:35 AM
I'm thinking the woodruff key has moved as part of your troubles - I can't see the crank being bent given the circumstances. It's definitely a mystery it will be very interesting when you finally locate the cause.
No woodruff key on a 750 SOHC ;)
Post by: MrDavo on October 14, 2020, 12:13:12 PM
Whatever I am glad you are getting to the bottom of it, as the suspense is killing us.
This reminds me of when, as a teenager, I worked some evenings and weekends at a garage in Lancaster - even at school I had a Moggie Minor and a Triumph T100 to support. One day the boss asked me to come with him to help tow in a Mini estate that had clanked to a sudden halt in Galgate. We spoke to the lady driver, who told us that she had just topped the water up at a petrol station, and how it had taken ever such a lot to fill it right to the top. My boss asked her to show him where she had put this water, and she pointed to the oil filler cap on top of the rocker cover. :o
Post by: PJM47 on October 14, 2020, 01:19:33 PM
After lifting the crank in an out a few times the large starter gear has come loose and is now free to move on the taper shaft, I can move it latterly by 5mm or so, it spins freely (independently of the shaft) clockwise but not anticlockwise. Not sure what is going on there.
But with the starter gear now floating loose on the shaft and the crank back in the case, the crank now rotates freely and smoothly, phew, so I believe somehow that gear had got jammed against the case causing the problem.
I need to get the special generator puller tool before I can look any further, and how to fix it is not yet clear but I'm thinking we are pretty close now...
Cheers
Paul
Post by: Trigger on October 14, 2020, 01:25:17 PM
You have done this a little arse about face as, you should of taken the fly wheel off before splitting the engine ::)
Post by: philward on October 14, 2020, 01:29:51 PM
Sent from my moto g(7) power using Tapatalk
Post by: K2-K6 on October 14, 2020, 01:29:56 PM
That's the correct operation of it, a very clever "sprag" clutch that will spin the crank in one direction when actioned by the starter motor, but be completely free in rotation in the opposite direction. It stays still while the motor runs and is virtually frictionless.
It means the starter doesn't have to be engaged/disengaged unlike a car system.
Post by: philward on October 14, 2020, 01:33:34 PM
On the inside of the starter cog is a bronze bush, it is easy to see it that is damaged ;)Will be difficult to get it off now even with the tool due to holding the crank - should be doable but more difficult
You have done this a little arse about face as, you should of taken the fly wheel off before splitting the engine ::)
Sent from my moto g(7) power using Tapatalk
Post by: PJM47 on October 14, 2020, 03:44:39 PM
Managed to get the generator nut off, just waiting for the puller tool now.
Although the starter gear is now behaving more correctly (it didn't spin any direction before, only just realised that wasn't normal!) I assume there is still something wrong? In normal operation is that cog free to move a bit latterly. I assume it's not meant to be able to rub the case if it wants?
Post by: Bryanj on October 14, 2020, 05:02:14 PM
Post by: K2-K6 on October 14, 2020, 05:39:22 PM
Ok learning a lot here.
Managed to get the generator nut off, just waiting for the puller tool now.
Although the starter gear is now behaving more correctly (it didn't spin any direction before, only just realised that wasn't normal!) I assume there is still something wrong? In normal operation is that cog free to move a bit latterly. I assume it's not meant to be able to rub the case if it wants?
There's a sectioned schematic of it in the original 750 manual (doesn't appear in last one) that may help, check Ash's dropbox stash for a look. If not there I can photo and post from mine.
Post by: Bryanj on October 14, 2020, 08:25:47 PM
I think the owner might like to look at the job lot of 750 parts in another thread where at least one of those cranks sould be usable
Post by: PJM47 on October 15, 2020, 08:15:13 AM
There's a sectioned schematic of it in the original 750 manual (doesn't appear in last one) that may help, check Ash's dropbox stash for a look. If not there I can photo and post from mine.
Thanks, found the one in Ash's dropbox, much clearer.
Post by: PJM47 on October 15, 2020, 03:52:33 PM
So do just put it all back together now? Perhaps the starter gear was just seized up a bit from when there was no oil? It's all free now anyway.
I'll replace all the seals and gaskets, anything else worth replacing/checking whilst its apart? Nothing is in particularly bad condition, little bit of wear on some of the main bearings. I leak tested the valves and all seems good is it best to leave those alone?
Post by: paul G on October 15, 2020, 04:03:44 PM
Primary drive chains and cam chain if they need it.
Why would you want to tear it down again.
Lapping in the valves is a simple job and replacing the valve stem seals is a no brainer :o they are in the gasket kit anyway.
Post by: Trigger on October 15, 2020, 05:37:05 PM
Look at changing the primary chains, cam chain to a up graded FTH DID, all the o,rings, including oil pump and inspect the primary chain tensioner to see if it has gone hard and brittle, check the cam chain tensioner, mid wheel and cam blade for brittleness, cracks or chips. Check the piston rings are not suck in there groves and turn easy. I would throw another set of rings on to be on the safe side and they can be bought for around £40 for a full set. Always use a top quality gasket set and upgrade the O'rings that are in the kit.
Put the crank on a bench and put all the rods on in the correct order and the right way round, torque them up and make sure they turn on the crank very easy with no tight spots ;) Build up the bottom end first and test everything before even temping to put the top end on.
We like pictures so, loads of photos as you go and we can advise if something is not quite right.
Post by: PJM47 on October 16, 2020, 04:29:56 PM
Any recommendations as to a good gasket set and piston ring set? DS spares seems to be out of stock on both. There's a few on ebay but I've no idea of quality.
e.g.
https://www.ebay.co.uk/itm/Honda-CB750K-Four-1969-1978-Complete-Engine-Gasket-Seal-Rebuild-Kit/112709539389?hash=item1a3e03163d:g:SMcAAOSwN7pamvaM
https://www.ebay.co.uk/itm/Full-Gasket-Set-For-Honda-CB750F1-2-K1-7-SOHC-1970-1978/121817106884?hash=item1c5cdd89c4:g:H5MAAOSwrklU2js3
Post by: MrDavo on October 16, 2020, 04:50:57 PM
Following advice on here, I got a genuine Honda head gasket from CMS, it cost more than the whole Vesrah set. Worth it for the peace of mind in my opinion, as has been said you only want to take the engine out once.
Post by: Trigger on October 16, 2020, 05:16:13 PM
If you need seal kit, cam chains or any upgraded O'rings then, ask Nurse Julie.
For rings: These are cheap but they are Riken and i have fitted over a 100 sets of these >>> https://www.ebay.co.uk/itm/69-76-HONDA-CB750K-STANDARD-PISTON-RINGS-SET-4-RINGS-INCLUDE-11-CB750KPR/254040843680?hash=item3b2603a5a0:g:D0MAAOSwfQRXMPEZ
Post by: paul G on October 16, 2020, 07:45:25 PM
As PaulG has said, you are in there and you don't want to take it apart again as Paul G knows very well ;)In my defence it wasn’t through skimping on parts :D all I can say is my engine came in a million parts and 5th gear fits both ways and only one is correct :(
Look at changing the primary chains, cam chain to a up graded FTH DID, all the o,rings, including oil pump and inspect the primary chain tensioner to see if it has gone hard and brittle, check the cam chain tensioner, mid wheel and cam blade for brittleness, cracks or chips. Check the piston rings are not suck in there groves and turn easy. I would throw another set of rings on to be on the safe side and they can be bought for around £40 for a full set. Always use a top quality gasket set and upgrade the O'rings that are in the kit.
Put the crank on a bench and put all the rods on in the correct order and the right way round, torque them up and make sure they turn on the crank very easy with no tight spots ;) Build up the bottom end first and test everything before even temping to put the top end on.
We like pictures so, loads of photos as you go and we can advise if something is not quite right.
Post by: PJM47 on October 16, 2020, 08:13:28 PM
I’ll go for cam chain as well so will need that and if there’s upgraded o rings that help sounds like a good idea.
Not sure if I need primary chains yet, they are quite expensive..
Post by: philward on October 16, 2020, 08:30:24 PM
Bloody expensive these rebuilds
Post by: Trigger on October 17, 2020, 07:44:17 AM
Post by: royhall on October 17, 2020, 07:23:01 PM
Post by: PJM47 on October 19, 2020, 02:01:13 PM
Without wanting to start too much of a debate what's the best / recommended sealant for the bottom end? I've seen other posts but not really a conclusion.
Post by: Nurse Julie on October 19, 2020, 02:03:30 PM
so most bits on order now (ouch).Honda Bond, 3 Bond , Yam Bond etc for crank case halves only. The lightest, lightest smear, so light, you can almost see through it.
Without wanting to start too much of a debate what's the best / recommended sealant for the bottom end? I've seen other posts but not really a conclusion.
Post by: McCabe-Thiele (Ted) on October 19, 2020, 03:34:12 PM
Post by: PJM47 on October 19, 2020, 04:23:01 PM
Having followed this post with interest I am none the wiser yet as to what the cause was - have I missed something?
No I'm not sure I am either. Like I say at the start of this page once the starter gear was removed everything freed up. Putting it back on and everything is still free, the crank spins nicely, even keeps turning on its own with a push, I could barely move it before. Putting the rods back on as Trigger suggested and it still all turns nicely.
As I say my only concern was I'm not sure if that gear is mean to be able to move latterly on the shaft a bit which it does now. I have nothing to compare it to and nothing looks wrong.
I'd have been much happier finding something broken but not sure what else can be done.
Post by: Bryanj on October 19, 2020, 04:30:29 PM
Post by: PJM47 on October 19, 2020, 05:17:37 PM
Put the alternator rotor on temporarily(i.e. bolt not tight) then see if it wobbles when crank is spun, i have seen the taper end bent
No wobble. Checked with fixed point on the case, not that accurate, but nothing obvious.
Post by: royhall on October 19, 2020, 05:24:33 PM
Post by: PJM47 on October 19, 2020, 05:30:45 PM
Post by: PJM47 on October 19, 2020, 05:35:22 PM
so most bits on order now (ouch).Honda Bond, 3 Bond , Yam Bond etc for crank case halves only. The lightest, lightest smear, so light, you can almost see through it.
Without wanting to start too much of a debate what's the best / recommended sealant for the bottom end? I've seen other posts but not really a conclusion.
Thanks, blimey Honda bond 4 is reassuringly expensive isn't it. Don't want it leaking though.
Post by: Bryanj on October 19, 2020, 05:55:41 PM
Sold a nos one to the states last year!
Post by: royhall on October 19, 2020, 05:58:07 PM
Post by: PJM47 on October 19, 2020, 08:33:42 PM
I wonder if the bush has pushed in/back slightly under the stress allowing the gear to move further up the shaft than normal and hitting the case and also getting stuck? On the plus side at least the gear can be replaced after the engine is back together.
First pic is mine, secon pic is a used one on eBay.
[attach=1]
[attach=2]
Post by: allankelly1 on October 19, 2020, 08:43:30 PM
Looks like a glacier bush to me
I have changed these on my RD350LC kick starter idler and the clutch centre bush so could be well worth while if it’s shot pressing it out and getting a size and asking a local bearing supplier if they could supply a new one
(https://uploads.tapatalk-cdn.com/20201019/df0b2ffa8da3a8d003aa010514332dd9.jpg)
As then the bush and gear would be as good as new
Sent from my iPhone using Tapatalk
Post by: PJM47 on October 19, 2020, 10:15:11 PM
Hi
Looks like a glacier bush to me
I have changed these on my RD350LC kick starter idler and the clutch centre bush so could be well worth while if it’s shot pressing it out and getting a size and asking a local bearing supplier if they could supply a new one
As then the bush and gear would be as good as new
Sent from my iPhone using Tapatalk
Interesting thanks. I will look into it.
Post by: Trigger on October 20, 2020, 12:23:26 AM
Post by: royhall on October 20, 2020, 08:18:08 AM
Note it was definitely the starter gear that was the problem, then crank was in and out several times and fully oiled and nothing else connected, it was just resting on the bottom shells but it still would not turn freely. On one of the occasions of taking the crank out the starter gear came loose a bit and then everything was instantly fine after that. Still seems very odd to me.Looks like you found the smoking gun then. The wheel should not have been stuck to the crank it should be free to rotate. Amazing what lack of oil does to an engine. It is free to slightly move on the boss and is fed by pressurised oil to the bush and to behind the wheel through a feed hole. Make sure everything is straight before reassembly as those starters on a good battery put out a lot of torque.
Post by: PJM47 on October 20, 2020, 07:18:42 PM
Do we think I need to give the cylinders a light hone to put cross hatching back to settle in the new rings or is best to leave as is?
Post by: Greg65 on October 21, 2020, 03:30:05 PM
Cheers,
Greg
Post by: PJM47 on October 23, 2020, 02:52:54 PM
Post by: Bryanj on October 23, 2020, 04:15:56 PM
Post by: PJM47 on October 24, 2020, 03:30:45 PM
On to the main bearings, please could people advise on whether they think these should be replaced, I know not easy to tell from the pictures. Any help appreciated as always.
[attach=1]
[attach=2]
Post by: Bryanj on October 24, 2020, 04:06:51 PM
Considering the marks on the mains i think its worth splitting the big ends and inspecting.
Its all work and more expense but these motors need doing right
Post by: PJM47 on October 24, 2020, 04:23:18 PM
If anyone has a source of bearings cheaper than £15 a shell that would be good :)
I think I have worked out the codes, BABBB on the case and AAAAA on the crank so I make that 4 greens and a yellow.
Big end bearings all look pretty good, much better than the mains.
Post by: paul G on October 25, 2020, 07:22:14 AM
Post by: McCabe-Thiele (Ted) on October 25, 2020, 07:52:20 AM
yes what I thought. That centre one is the worst case and I will replace the pair. I was hoping to avoid having to replace them all though as they are so expensive, but maybe it's worth doing now. What seems like a no brainer job on this bike is always a hesitation as everything is so expensive.
If anyone has a source of bearings cheaper than £15 a shell that would be good :)
I think I have worked out the codes, BABBB on the case and AAAAA on the crank so I make that 4 greens and a yellow.
Big end bearings all look pretty good, much better than the mains.
When I worked on petrol engines (mainy on cars admittedly) it was pretty much routine that a crank removal led to replacing the crank & main shells. Even when the bearings didn't look that bad it was a case of well my labour is free so why skimp on the material costs bearing in mind the amount of effort involved in dismantling the engine again.
I also found that replacing piston rings under the same argument was not as effective unless there was a very good reason such as poor compression, visible damage such as a broken ring or piston lands plus of course bore scoring / excessive oil consumption.
Likewise I have never been a fan of glazebreakers after over doing it once resulting in needing a rebore. I would prefer to have a rebore if the aforementioned issues were found. I also learnt to my cost that there was a wide range of competency in machine shops that did rebores. In the 1970's there were something like 8 or 9 firms in the Derby area that carried out engine machine work. Some firms seemed to live on reputations that were not maintained over time.
If I have to have a rebore on my bike I would struggle to know anywhere locally as I am now out of the circle of local knowledge - I haven't had an engine rebore since 1979. Irrespective of the distance from me I would in all honesty place my trust in someone such as Trigger as he has what I perceive as that rare combination of reputation, skill, pride in his work with a love of what he does.
Post by: Bryanj on October 25, 2020, 09:39:41 AM
Post by: philward on October 25, 2020, 12:29:19 PM
Post by: taysidedragon on October 25, 2020, 12:47:59 PM
Had a 1200 Anglia that had a 'rubber crank' - 3 main bearings - centre bearing always knackered (was that a Kent or Essex or none at all?)
Same engine as a Ford Model T! 😁
I t-boned a Ford Anglia with my Bonneville in the seventies and the car came off worse. The paint was holding the bodywork together.
Post by: cliff7 on October 25, 2020, 01:09:31 PM
Had a 1200 Anglia that had a 'rubber crank' - 3 main bearings - centre bearing always knackered (was that a Kent or Essex or none at all?)
Kent engine. 1340 fitted to Consul Classic was even worse.
Post by: Bryanj on October 25, 2020, 02:45:08 PM
Post by: PJM47 on November 01, 2020, 03:05:59 PM
[attach=1]
[attach=2]
Just waiting new chain tensioner and an o ring for that front tube.
Post by: PJM47 on November 01, 2020, 03:11:50 PM
[attach=1]
[attach=2]
Post by: Bryanj on November 01, 2020, 03:36:17 PM
Make sure no raisedbits and try it
Post by: K2-K6 on November 01, 2020, 04:02:03 PM
Talking about "selotape" coating level (from aerosol) to let dry before assembly and degrease faces with carb cleaner or isopropyl alcohol just prior to installing.
Post by: Trigger on November 01, 2020, 08:19:10 PM
Not so keen on this. Looks like it has been hacked with a screwdriver by someone trying to open it. The top end has been off before. It was covered in sealant as well. Do we think this will seal ok with new gasket?
(Attachment Link)
(Attachment Link)
Are you sure that those barrels have not been decked ? As i can see markings from a head skimming machine.
Post by: PJM47 on November 01, 2020, 09:54:29 PM
As long as we think it coukd be ok, may be with a bit of hylomar that’s a relief.
Post by: Bryanj on November 02, 2020, 08:51:51 AM
Post by: PJM47 on November 02, 2020, 04:10:00 PM
Should you try the Hylomar a BIT is the important part!!!!
Ok noted. Or do we think I am better off not using any sealant at all? Opinions vary.
Post by: Bryanj on November 02, 2020, 04:42:01 PM
Post by: Trigger on November 02, 2020, 05:23:16 PM
What jets does the head have fitted ?
Post by: PJM47 on November 02, 2020, 05:45:55 PM
It was sealed OK before you took it apart without anything. I would never use any sealant on any gaskets as, the 750 is prone to the oil jet blocking with sealant and bang goes the top end ;)
What jets does the head have fitted ?
Not sure, is this the jet you mean:
[attach=1]
Post by: Bryanj on November 02, 2020, 06:58:25 PM
Post by: K2-K6 on November 02, 2020, 07:20:18 PM
Purpose is to restrict the oil flow to designed rate while maintaining pressure within crankshaft supply architecture, the cam area being low pressure as opposed to the crankshaft being high.
It's the nature of any restriction in flow that it will "collect" any stray particals (it's only fed filtered oil) resulting in impaired flow or blocking.
The risk here is to have detached and excess sealant pass onward up from gasket face and get stuck in those small restrictions.
It's your appreciation of this as to the decision you make, blocked they will certainly trash their onward valve train, of that there's no doubt.
I've used Hylomar spray as stated above (light spray of gasket and leave to dry) to leave a "selotape" quantity fine film on the gasket. This primarily on the F2 engine as they are very prone to oil seeping at the head gasket, this never with any problems.
I can see the other point or view and wouldn't argue with the logic, but know that many owners fret about any oil leak at all here at this juncture. It's highly unlikely to compromise the compression sealing of the engine (with no sealant applied) so not a worry from competent running perspective.
Of course if it does leak it's just that normally and not drastic, versus the other risks. But naturally it's engine out to correct.
Giving a clear picture hopefully will help
Post by: PJM47 on November 02, 2020, 08:26:24 PM
Having had various old British bikes I’m not too concerned about oil leaks.
I will make sure those jets are clean before putting it back together.
Post by: Trigger on November 03, 2020, 02:20:42 PM
Post by: PJM47 on November 03, 2020, 06:37:08 PM
These should not leak if the studs are sealed and the O'rings are up graded ;)
Are the o rings that come with the vesrah 156 any good? If not would you be able to point me at suitable upgraded ones please?
Post by: Nurse Julie on November 03, 2020, 08:17:29 PM
I have stock of all the upgraded O rings you need Paul. I will PM you after I've cooked dinner 😁😁😁These should not leak if the studs are sealed and the O'rings are up graded ;)
Are the o rings that come with the vesrah 156 any good? If not would you be able to point me at suitable upgraded ones please?
Post by: PJM47 on November 06, 2020, 10:33:54 AM
These should not leak if the studs are sealed and the O'rings are up graded ;)
Trigger of you get a second would you be able to elaborate on what you mean studs are sealed? How would I do this? I have the upgraded O-rings now. Ta.
Post by: Nurse Julie on November 06, 2020, 12:32:29 PM
Post by: PJM47 on November 06, 2020, 06:49:55 PM
The head studs that can leak are the ones that the towers slide over and they have a M6 washer and M6 nut. If the stud thread is not sealed with thread lock, oil can weep down the thread to the spark plug area.
OK thanks
Post by: PJM47 on November 17, 2020, 05:13:21 PM
I’m getting ready to put the engine back in, I thought first I’d hook up
the oil tank and try to see some oil flowing. But I am struggling to get pressure, I am turning it on the starter, as much as I dare not wanting to damage it, and all
looks good but I’m not seeing much or any oil get to the top end.
I’ve read this is not unusual with air locks in the pump. But I am not sure now whether to just put the engine back in the frame and sort it later or persevere with it on the bench. Opinions vary on what do.
I tried priming the pump but its not really possible with the engine vertical for access. I filled the oil gallery and that didn’t help, tilted it to the side, didn’t help.
Any thoughts appreciated.
Post by: MrDavo on November 17, 2020, 06:18:25 PM
I took the oil pump apart and packed it with the stuff, then tried again. Instant success! Oil appeared in the oil gallery at last, then in the cambox. I believe some old American V8s use the Vaseline technique as a matter of course to get their oil pumps started. The jelly simply dissolves into the oil, and wont damage or block anything. One wonders if Honda did something similar at the factory, I recall reading that they came primed with some sort of fishy oil that had to be replaced before use, the ex Honda workshop guys on here may be able to confirm that.
There was also a very sad thread on here from a member who put all his effort and money into a rebuild, then started his CB750 up without checking for oil pressure. the result was a beautiful rebuilt bike with a freshly ruined motor. :( As I remember it he was too disheartened to pull the engine to do it all again, and sold the bike 'as is' for someone else to fix.
Post by: Trigger on November 17, 2020, 06:42:09 PM
You should not try to turn the engine on the starter motor until you have oil pressure up or you will damage the shells. Lets hope you put bearing guard on the shells when yo assembled the engine ::)
Post by: allankelly1 on November 17, 2020, 06:52:07 PM
After a complete failure to get any oil pressure in my CB750K1 engine after I rebuilt it, a worried query on here sent me off to Boots to buy a tub of generic Petroleum jelly (it doesn't have to be Vaseline by brand).Yes packing the pump with Vaseline is standard practice when building Rover V8 engines so the pump can prime itself
I took the oil pump apart and packed it with the stuff, then tried again. Instant success! Oil appeared in the oil gallery at last, then in the cambox. I believe some old American V8s use the Vaseline technique as a matter of course to get their oil pumps started. The jelly simply dissolves into the oil, and wont damage or block anything. One wonders if Honda did something similar at the factory, I recall reading that they came primed with some sort of fishy oil that had to be replaced before use, the ex Honda workshop guys on here may be able to confirm that.
There was also a very sad thread on here from a member who put all his effort and money into a rebuild, then started his CB750 up without checking for oil pressure. the result was a beautiful rebuilt bike with a freshly ruined motor. :( As I remember it he was too disheartened to pull the engine to do it all again, and sold the bike 'as is' for someone else to fix.
Sent from my iPhone using Tapatalk
Post by: K2-K6 on November 17, 2020, 07:48:24 PM
Also if you want to observe for initial flow, the pump goes straight to the oil filter housing which you can look at without the filter on to see if you've any output at all. As soon as you can see it coming through that pipe you know the pump head is operating and filled with oil.
If present there, it will have to fill the housing then go through the filter to enter the feed galleries via the centre of the bolt.
If you take the oil filter housing off and it's dry, then it confirms the pump is air locked.
Post by: PJM47 on November 17, 2020, 08:13:57 PM
Post by: K2-K6 on November 17, 2020, 08:29:31 PM
So if nothing comes out at all, then you'll never get pressure anywhere.
You've literally got to see it delivered through there, then that confirms the pump is pumping oil. Put the filter assembly back on and it should then fill and deliver through the whole system.
Post by: PJM47 on November 17, 2020, 10:14:59 PM
Ta
Post by: K2-K6 on November 17, 2020, 10:54:47 PM
It's usually from empty pump and pipes to and from that it just won't suck.
Post by: K2-K6 on November 17, 2020, 10:59:05 PM
Yes packing the pump with Vaseline is standard practice when building Rover V8 engines so the pump can prime itself
Sent from my iPhone using Tapatalk
A fine engine, one of my favourites. Have you an interest in them?
Post by: allankelly1 on November 17, 2020, 11:35:16 PM
Built a Dax Rush with a 4l Rover V8 in
Engine built by myself and Dave Ellis and as you can see was not in standard tune
(https://uploads.tapatalk-cdn.com/20201117/60279e5012d8fcc9e0cd3a9ca5c4d7de.jpg)
(https://uploads.tapatalk-cdn.com/20201117/b73cccebf3c50e0ef75adf5868d00339.jpg)
Car weighted in around 650kg as a total kerbside weight as due to the the Rover being an all aluminium block and heads the engine only weights in at only 212 kg for a 4L lump (around the same weight as a Ford 2L pinto) so nice power to weight ratio
Fun but needed to be respected as it could bite you in the arse in a blink of an eye
Post by: McCabe-Thiele (Ted) on November 18, 2020, 08:07:29 AM
Back in the late 1970's a good friend of mine fitted his Ford Granada Mk1 with a Holley 4 barrel Carburetor fully upgraded rover V8 engine after extensive changes to the bulkhead plus fitting a Jaguar (IRS) rear axle.
It was a beast to drive and a tad happy at the back end especially in the wet.
Post by: philward on November 18, 2020, 08:40:09 AM
Sent from my moto g(7) power using Tapatalk
Post by: allankelly1 on November 18, 2020, 10:45:16 AM
Always loved the more purposeful look of the Dax Rush
Took some time to build and started with the engine first which took a year to build and cost in excess of 6k by itself
as it was built on a brand new short block and it had lots of one off bespoke parts made by myself like the thermostat housing and a one off pulley setThen once engine / box was built then bought the kit and again spent again a small fortune
(https://uploads.tapatalk-cdn.com/20201118/5563927ece5b7ffbaa58a6653ea56227.jpg)
(https://uploads.tapatalk-cdn.com/20201118/f5c8938eec22d4dda0a9266d271d589e.jpg)
(https://uploads.tapatalk-cdn.com/20201118/00de0c8933c30bbbbe13b2bfa630565e.jpg)
(https://uploads.tapatalk-cdn.com/20201118/7d6e5e8c0b4f191cdf0c08c5ad873fa4.jpg)
Was sorry to see her go and had a tear in my eye but replaced the empty space in the garage with motorbikes instead as you got to have something to tinker with
Sent from my iPhone using Tapatalk
Post by: PJM47 on November 18, 2020, 05:25:02 PM
I took the oil filter off and oil soon started coming out. Put it back on and within a few seconds oil came out at the top end and then all over my bench and the floor as I hadn’t noticed it was working. Not sure whether taking oil filter out and back in helped or just coincidence but it’s working now so all good.
Post by: K2-K6 on November 18, 2020, 09:46:22 PM
That looks excellent.
I took the oil filter off and oil soon started coming out. Put it back on and within a few seconds oil came out at the top end and then all over my bench and the floor as I hadn’t noticed it was working. Not sure whether taking oil filter out and back in helped or just coincidence but it’s working now so all good.
Good news then :) it's always a little concerning and nervous time if you don't see it coming up as expected.
The bleed through, I suppose it's logical in that the system when closed with filter housing in place will run at 60psi with oil in it. So resistance to pumping the oil supply against air pressure may be just sufficient enough to prevent the oil filling the pump head (classic air lock) with the pump unable to draw oil through by trying to pump air, if that makes sense.
In reality, with the filter off and if the oil was warmer it would in all probability nearly run through there under gravity.
Nevertheless, it's the earliest point you can check for oil pump output to see if it's really pumping anything, and easy to do to. As you found, once the pump is going the rest will fill quite quickly.
Post by: PJM47 on November 18, 2020, 10:02:45 PM
Post by: PJM47 on November 28, 2020, 05:29:32 PM
I replaced all the carb float needles and seats and overflow pipes to fix the original problem.
Many thanks for everyone’s help along the way.
Paul
Post by: Johnwebley on November 28, 2020, 06:09:16 PM
Enjoy it when you can
Sent from my SM-A750FN using Tapatalk
Post by: Laverda Dave on November 28, 2020, 07:55:42 PM
Post by: philward on November 28, 2020, 09:10:42 PM
Just to finish this one off, engine is back in and running beautifully! Sounds really good, think it needed an overhaul anyway.
I replaced all the carb float needles and seats and overflow pipes to fix the original problem.
Many thanks for everyone’s help along the way.
Paul
Good to hear its sorted Paul
Post by: royhall on November 28, 2020, 09:24:29 PM