Author Topic: CB750F2 .... silk purse from a sows ear.  (Read 3981 times)

Offline Bryanj

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #150 on: October 10, 2018, 01:06:22 AM »
Got a set of 550k3 carb bodies you cab have cheap plus postage, i know that a lot of the internals are the same but not sure on the bodies. Have you got the pilot jets out to clean them? They clog up for a passtime, are a press fit and you need to twist and pull with vice grips

Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #151 on: October 10, 2018, 08:31:55 AM »
Thanks Bryan....I'll do do e research and find out if the bodies are the same. Aside from the crack ..the carbs are not bad. Not taken the smaller jets out yet. Much still to do!
CB750F2 - in pieces
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Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #152 on: October 10, 2018, 12:43:49 PM »
Mixed dasy today. No work as I had a dentist appt...so some sneaky work was done on the motor.

Picked up a replacement impact driver as it was £8 to get the bit I needed....or £15 for a whole new one from Halfords with a lifetime guarantee. So....no brainer really. I got a few extra bits to replace ones that had been lost over the 30 years I had the tool...

It is only when you replace a worn out old tool with new that you realise how much slop has grown with time. New driver...3 taps...2 screws out. WOW. Didn;t even need a big hammer.

Flushed with success and with half an hour to spare, out came all the top bolts and into the prepared piece of card with the holes laid out...Flipped motor over. Lost the little screw in the top of hte neutral indicator thing I can't shift from the upper case...must go find that later. Undid all the bottom case bolts, breaking the torque in a sensible stress relieving pattern....gave the cases a few judicious taps on the big bits where the engine mounts are. Saw it shift. One section wouldn't budge. Resist the urge to 'pry' as I have seen a couple of minor scars on the cases where someone did...Find the bolt I forgot to undo after I slackened it...which forced me to turn the motor back over to get to it...then back over again...and hte cases parted like the Red Sea before Moses.

The Halleluia Chorus was playing on the MP3 and hte sun came out from behind the clouds.....

Nothing horrid met my eyes. I have not had time to check the shells or actually lift the crank out as I was now late for the appointment...but I am sure they understood. No time for photos either...so will do that later.
what I did have time to see was the state of hte crankshaft journals.

I had feared something looking like an aerial photo of a railyard.....rust....furrows....metal fragments. All these things were not there.

Instead, I could see a shadow line where the oil channel is in the shells, which was wiped with a lint free cloth....revealing a polished surface of shiny loveliness. I could not see a mark on the bearing surface. Not one. Which is how it should be. Running a fingernail across was smooth on all 4. That's a relief. Really is. Big ends all felt rock solid.

Of course...I haven't measured the clearances on the shells ( I have heard of Plastigage....understand the process...but it's not something I have ever done.  )

Also...I am reluctant to mess with the big ends, as they all seem smooth and free from any slack I can detect. Should I? Or should I not. Bottom end on this thing looks really tidy aside from the gorilla knackered primary sprocket shaft and some idiot marks on the cases .

Also need some gasket sealant for reassembly ( Hondabond isn't it ? ... won't have instant silicon stuff anywhere oil lives )

After the last couple of days of hassle...today has started well.

Aside from the dentist.
CB750F2 - in pieces
CB900F Hornet - the daily transport

Offline Oddjob

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #153 on: October 10, 2018, 06:29:04 PM »
Was in my local Honda dealer the other day, my mate who I worked with at QPM still works there, so I thought I'd ask him if he had some old tubes of Hondabond lying around as I needed a bit. Seems they don't use it, all the mechanics there prefer to use Yamabond instead. Not sure why but the tube they showed me cost around £35 and it was very large, maybe it's a bigger tube for roughly the same cost as Hondabond so it's better value.
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Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #154 on: October 13, 2018, 12:44:43 PM »
Stripdown is very, very nearly finished....and I am at the take stock stage....

I only have that annoying roll pin to get out to free off the kickstart shaft and the cases will be bare. How in the name of god does that thing come out? Do you just ruin it with molegrips...or can it come out in a state where it can ever go back in again. I assume they are available...
The other 'sticking point' is this damn thing...

Which seems fused on the shaft. Much WD40 and waiting. I have budged it around half a mill....if that. The soaking continues.

Had a good look at hte bearing shells in teh harsh light of day.




Don't look too bad, with only one of them really showing signs of wear. Don;t know whether they need replacing or if they would be OK to re-use.

Crank looks good...



Less good, with them free from their prison...is the rods. Quite a lot of surface rust. I assume this is a relic of standing long time. The rods themselves would only have got splash lube, and once the oil dried off...they were sitting in fresh air. The bores were fine, but....not the rods. Big ends feel smooth with no slop or noises. So....can these go back in...or do I need to budget for fresh. I'm out of my comfort zone here!

While I was in.,.I did notice something odd. I guess this might be further evidence ( if any were needed ) that someone was in here before me. The damaged clutch shaft...pry marks on the cases...and this. I assume the Japanese do know that 4...comes after 3.... Not here. By rods are labelled 1...2...3...and 3. That's not factory fit surely.

I also noted the pistons look more worn than I recalled when i popped the barrel off. I guess teh shiny oil has wiped away and with them in good light ( as in...not on the rods) it's a lot easier to inspect them. I have refitted worse....but that's something else I need to think about.

The crankshaft oil seal on the end was utterly buggered. I would be surprised if it kept oil in very well. Not as bad as the final drive seal though. The dried up chain grease was doing a better job of sealing than the rubber part.

One last thing.

I noticed a bit of marking on the bearing surfaces where the roller bearings for the gearbox and final drive sit. Is this normal? At some point some of those bearings look to have shifted. Do they need a few drops of bearing fit on assembly? Or has the case not been gripping them due to other issues? It's something I do not want to happen again.

Now to sit down and start writing up the shopping list.....and work out how long I am going to have to save up to afford what I need to do.
CB750F2 - in pieces
CB900F Hornet - the daily transport

Offline Trigger

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #155 on: October 13, 2018, 01:52:40 PM »
Nothing wrong with those rod numbers, it is the letter code that is important as this is the weight and should be all the same  ;)
The roll pin can be a bugger sometimes, if you can't get it out with grips then, tap a thread down the middle, insert a bolt and pull. If you bugger it, don't worry as i have a tray full of NOS ones.

Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #156 on: October 13, 2018, 02:02:57 PM »
Good idea on the thread thing....I'll give that a go.
Also handy to know where I can get one if I mangle it!

I'll also check the letter codes on those rods.

Not going to leave the kickstart in place as I want to properly wash, strip and paint the cases and that means no roller bearings around!
CB750F2 - in pieces
CB900F Hornet - the daily transport

Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #157 on: October 16, 2018, 12:04:23 AM »
Today...the engine strip was finally complete.

The pesky pin needed mole grips to 'squash' it enough to get it free. It's out....but it will need replacing. Tried threading it....was perfect for an M4 ... but the bolt wasn't able to handle the pressure and every M4 bolt I put in just stripped as soonas I put it under load. Brute force won the day.

Similar appraoch with the gearbox sprocket. That finally succumbed to a combination of penetrating fluid and violence. It was REALLY stuck on the splines. Had to come off though. The dust seal was shot and wasn't seated in the cases right. Grit had clearly got past it as the large bearing was making that grinding noise bearings make when they want to be thrown away. The smaller inner bearing was notchy too. See no good reason to put a rough bearing back in the cases....don't plan on pulling it all apart again that soon!

Packaged everything up, cleared the decks and tidied up. Next job is to strip the chipped and flaky paint off the cases, clean them back and get a coat of black engine enamel on.

I also have to put together parts list no1 .... the bits to replace for the bottom end.

1) Primary chains...more slack than there ought to be
2) Primary chain tensioner... the spring was weak and the wheel rock hard.
3) Camchain. Why not.....as the crank is out.
4) Final drive bearings & seal
5) crankshaft end seal.
6) roll pin for kickstart.
7) 4 new screws for gearshaft bearing carrier.
8) Any o-rings lurking around...there are a couple between the cases.
9) Order gasket set & Hondabond

Jeez...long list! I was expecting the project to soak up a couple of grand before I was done....with the largest slice of that going into the engine. So here goes.......
CB750F2 - in pieces
CB900F Hornet - the daily transport

Offline Trigger

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #158 on: October 16, 2018, 06:30:29 AM »
1) Primary chains...more slack than there ought to be >> I always replace as, you don't want to be going in the bottom end again.
2) Primary chain tensioner... the spring was weak and the wheel rock hard.>> Once hard they start to get little chips.
3) Camchain. Why not.....as the crank is out. >> Upgrade with a FTH and check the midwheel, tentioner and guide.
4) Final drive bearings & seal >> Check all the bearings in the gearbox and the clutch lifter bearing.
5) crankshaft end seal. >> All seals come in a engine seal kit.
6) roll pin for kickstart. >> PM me your address and i will pop one in the post.
7) 4 new screws for gearshaft bearing carrier. PM me and i will pop a set in with the roll pin.
8 ) Any o-rings lurking around...there are a couple between the cases.>> There are a few o'rings that will need replacing, 1 on the main oil gallery bungs and 2 on the bottom bungs, 1 on main oil gallery blanking bung, 1 on the neutral switch, 1 around the crank case dowel, 1 on the clutch lifter rod. 1 on gear shaft carrier ( I always upgrade these to viton )
9) Order gasket set & Hondabond >> The engine will leak oil without them  ;) ;D
10) You will also need a oil pump rebuild kit.
11) Don't try to remove the engine studs unless they are very rusty  ;)
« Last Edit: October 16, 2018, 06:34:16 AM by Trigger »

Offline paul G

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #159 on: October 16, 2018, 08:08:16 AM »
Coming along nicely  :D As Trigger said replace ALL the gearbox bearings (I did) false economy not to as in the grand scheme of things not that expensive and you don't want to be going back in in a couple of years  :o :o Trigger may have them if not Yamiya are cheaper than Silver even with the post and capture fees.
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Offline UK Pete

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #160 on: October 16, 2018, 10:06:46 AM »
Great work love your enthusiasm , the engine can swallow sooooooo much money it's a case of if you you do one thing you have to do the lot then all of a sudden 2 thirds of the budget had gone on things you can't even see


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Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #161 on: October 16, 2018, 10:44:59 AM »
Do I need a bearing puller to get the bearing out of that layshaft bearing holder?

Cosmic. Just great . .... My PC is dead. PSU has failed I think.  But it means my only internet access is by phone now. That's delayed my part ordering to next month then 😭
« Last Edit: October 16, 2018, 11:00:32 AM by SumpMagnet »
CB750F2 - in pieces
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Offline hairygit

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #162 on: October 16, 2018, 12:20:41 PM »
Do I need a bearing puller to get the bearing out of that layshaft bearing holder?

Cosmic. Just great . .... My PC is dead. PSU has failed I think.  But it means my only internet access is by phone now. That's delayed my part ordering to next month then
Don't panic, a PSU can be found on e bay for reasonable money, and are very easy to fit, you're looking at £15-20 for a decent one including delivery. 4 screws hold the PSU in place, all you do is undo the screws, the PSU comes out from the inside of the casing, screw the new one in place, then swap the plugs into the motherboard one at a time, that way you can't go wrong. When all of them have been swapped over, lift the dead unit out of the casing, refit the side, plug into the mains and you're done.

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Offline Trigger

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #163 on: October 16, 2018, 01:34:44 PM »
Do I need a bearing puller to get the bearing out of that layshaft bearing holder?

Cosmic. Just great . .... My PC is dead. PSU has failed I think.  But it means my only internet access is by phone now. That's delayed my part ordering to next month then 😭

Very easy to get the bearing out of its housing, pop it in the oven for 10 min and tap it out on a block of wood  ;)

Offline SumpMagnet

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Re: CB750F2 .... silk purse from a sows ear.
« Reply #164 on: October 16, 2018, 09:57:54 PM »
PSU problem sorted :) The fan had failed, and it was stalling...causing the unit to trip out. Wasn't overheating...just pulling too much current..and there must be a trip out in there that was popping. Cut out and soldered in a new fan. 5 minute job. That sorted that. Then I found I had another problem on top of that ...which I traced to a Win10 update. Causes a misdirection to the boot ini....leading to a 'boot device not found' error. Had to manually remove the package in DOS ( I am old enough to have used this before! ), boot into safe mode and upload the fix patch. Wasted half a day....but it cost me nothing.

I'm on safe ground when it comes to PC components...and electronics in general...but thanks for the tips HairyGit :) I was more stressed by the possible side issues of a fried PSU. Last time I blew a PSU it spiked the motherboard and it was toast. The thing is about 5 years old...so you then have to weigh up whether it's worth buying a motherboard for outdated CPU and RAM....and before you know it...£800 has piled onto the credit card. Money I want to spend on the Honda!

Still...on the plus side....my primary chain sprocket arrived today. £30 plus postage. The guy was selling it with a pair of chains and a tensioner. Both used...but he wasn't keen on splitting. Originally he had wanted £40...but a bit of haggling and I was happy. It's in decent condition and certainly as good as the one I have taken out. I guess the guy didnt want to get stuck with a chain and tensioner nobody would ever buy. I now have 2 sets of worn chains and 2 tensioners with saggy springs and hard as concrete wheels. Ain't I the lucky one :)
CB750F2 - in pieces
CB900F Hornet - the daily transport