Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: royhall on June 29, 2022, 04:39:27 PM
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Just reassembling the 750 top end and hit a weird problem. Everything has gone fine getting the cam towers/cam/cam-chain assembled but when I come to put the inlet rockers on they are tight. The adjustment screws are backed right off which gives about 6mm of play on the exhausts, but the inlets are so tight they wont go in at all. I am using the original valves and springs, the seats weren't recut just a very light lapping in. I am aware that the cam needs to turn away from the lift area to get the follower on so it's not that. With a straight edge on the valves they are all virtually the same height. What the heck have I done wrong I'm stumped, I'm hoping I have missed something obvious that's easy to rectify.
I thought that somehow the valves may be sitting too high but according to CycleX the compressed spring length should be 37mm and valve stem protrusion should be 43mm. All four of the inlet valves measure bang on the money?
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I know you're aware you need to turn the cam but have you actually turned it? By the photo, it looks like #3 lobe is facing up. The cam caps also need to be fitted before you put the follows in.
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The photo was taken as I was stripping it down again, the cams had probably been turned. Something drastic has happened here (probably me again) so going to reverse a bit and see what's happened. It will be obvious when I find it. All part of the fun eh, at least I haven't broken anything.
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There are so many things you have to go through just to stop these heads from leaking and it is not in any manual.
1) Re seal the cam tower studs in the head with a stud lock / retainer or the oil will trickle down the threads.
2) Make sure that all the head seals are sitting proud of the head gasket as, most seals and o'rings that come in a after market gasket set are sized for a OEM head gasket and aftermarket are thicker.
3) Put Honda bond on the under side of the pucks around were they seal on the lip.
4) Once the head is on and torque down , leave for 24 / 48 hours and re-torque at 18 ftlb.
5) Lube up all cam surfaces with bearing guard.
6) set the tappets before putting the rocker cover on, making sure no tappets or valve tops are chipped
7) The last part fitted is the cam chain tensioner last and the setting is 5 degrees from TDC, which is were the spring is.
As for what you have done wrong, i have no idea ;)
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Thanks for the info Trig, I'm sure that will be a big help to a lot of people and not just me.
I did check the o-rings were proud of the gasket , but they were only just. As I'm going backwards now I will probably go a size thicker as the o-rings are taking full pump pressure there due to the flow restrictors in the head. That's easy with o-rings but what can be done about the 8 drain tube seals, are there longer ones available? The threads on the cam tower studs I have never considered so I will do that as well. I always use Threebond under the pucks, so that will be a nice clean up job. The tightening down I usually do at 50%, then 75%, then 100% and leave for a day then go round again to check.
As for the problem with the valves, thinking it through there is only one logical explanation. I think I know what has happened but will prove it this afternoon when I take the head back off. This is going to be another hard to live down senior moment. I have been doing ridiculous things for around the last two years and at 63 that's worrying, I'm defo heading for a Dementia ward at some point. Just in the last seven days:
1. Picked up my 5 year old grandson from school. He gave me his school bag for safe keeping while he played on the park. Two hours later a mad rush back to the park, fortunately his bag was still where I left it.
2. Did a landlords gas safety check at a house, everything was okay. Got a phone call an hour later to say no hot water. 12 mile round trip to turn the gas back on (I had to go in case I had forgotten to put the test nipple back on, fortunately I had).
3. Mrs H said "I have put sausages in the oven, turn them over in ten minutes I'm going for a shower". Completely forgot. Sausages black on one side ,uncooked on the other. Yummy.
I could go on but I think you get the picture. I will report back later when the engine is stripped back with the worrying verdict on both the engine and my present mental state. Got to go, nurse is calling it's time for my bath.
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Hilarious Roy! My brother in law was sent to the local shop for one thing, milk met in with one or two people on the way and yes came home with no milk. Certainly makes me feel better. Yesterday I had three alarms set on my phone, just in case. 😂
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It's not just you lot, I sat down yesterday to eat my lunch and looked down to find a tub of margerine on my plate and a bag of crisps!
I'd put the sandwich in the fridge.............. along with my truck keys, Doh, Morning! ;D ;D :o 8)
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A few weeks ago, I spent quite some time looking for my reading glasses and eventually found them in the fridge!
Worse still, a while ago I bumped into someone that I knew quite well and, as he was on the way to speak at a professional gathering, he asked whether he "looked the part". I said that it would be fine if he took off one of the two ties that he was wearing, to which he replied that his wife must have put the first one on in case he forgot and then whilst sat in the car, he had put another on without noticing.
He is a retired medical professional who held some quite senior posts when working!
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It's not just you lot, I sat down yesterday to eat my lunch and looked down to find a tub of margerine on my plate and a bag of crisps!
I'd put the sandwich in the fridge.............. along with my truck keys, Doh, Morning! ;D ;D :o 8)
Mmmm margarine dip Roo. 😂😂😂
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After reading the above replies it makes it easier for me to enter the confession box. I refer to my earlier post in mitigation.
Me: Forgive me Father for I have sinned.
Priest: Which of Gods laws have you transgressed my son.
Me: It is the holy law of SOHC father.
Priest: Go on.
Me: I had a senior moment and put the intake valves in the exhaust, and exhaust valves in the intake.
Priest: (Large sigh) According to Gods law "Thou Art a f***ing Dick Head"
Me: But,but,but.
Priest: Your penance is to spend the day stripping back to barrels and cleaning all up, then pay a forfeit of £51.35p to M&P for a holy top end gasket set.
Me: Thank you Father I am humbled.
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You don't need another gasket set Roy. If the engine hasn't been run, which it hasn't, you can use everything again.
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I considered it Julie but decided to stay on the side of caution and just replace the seals and gaskets. Already caused enough mayhem for this rebuild. Plus Trig was correct about the oil feed o-rings, the 11*2.5mm standard rings are not thick enough so am fitting 10*3mm.
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After reading the above replies it makes it easier for me to enter the confession box. I refer to my earlier post in mitigation.
Me: Forgive me Father for I have sinned.
Priest: Which of Gods laws have you transgressed my son.
Me: It is the holy law of SOHC father.
Priest: Go on.
Me: I had a senior moment and put the intake valves in the exhaust, and exhaust valves in the intake.
Priest: (Large sigh) According to Gods law "Thou Art a f***ing Dick Head"
Me: But,but,but.
Priest: Your penance is to spend the day stripping back to barrels and cleaning all up, then pay a forfeit of £51.35p to M&P for a holy top end gasket set.
Me: Thank you Father I am humbled.
You have cheered me up no end with your valve confusion - I feel slightly better about my plug lead confusion now.
PS
Don't forget the valve stem seals!
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Wow Roy; genuinely feel for you, what a complete pain.
Collectively there’ll be 10s of us on the forum going, “Phew, it’s not only me then”, and presumably now feeling a bit braver to, ahem, share!
Steve, perhaps, on this male dominated Website, a new forum is needed: “My Cock (up) is bigger than yours” ?
Hey Ho.