Engine full of fuel and seized up

[Bryanj]

The gear runs on the parallel bit of the crank, i have seen the clutch ass come loose on the back of the rotor but not often.
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

[PJM47]

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.

[PJM47]

Generator wheel and starter gear now removed. Can't see any problems with any of it. Only thing I'm not sure about is if the gear is meant to be able to move about a bit on the shaft.

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?

[paul G]

I think that would be a false economy not replacing the bits that you can while you are in there.
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  they are in the gasket kit anyway.

[Trigger]

As PaulG has said, you are in there and you don't want to take it apart again as Paul G knows very well 

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.

[PJM47]

ok thanks, will look at doing do all that.

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

[MrDavo]

I used a Vesrah gasket set, everything was there and fit fine, but the genuine head gasket is far superior, and has a 'sticky' finish which the pattern ones don't.

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.

[Trigger]

The gasket sets in the link are no good for early 750K's. You will need Vesrah VG156/556 for a early engine and i am out of stock of those. Phone Sliver and ask when he will have Vesrah gaskets back in stock but, make sure it is VG156 as he was selling VG158 for the early engine which was wrong 

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

[paul G]

As PaulG has said, you are in there and you don't want to take it apart again as Paul G knows very well 

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.

In my defence it wasn’t through skimping on parts all I can say is my engine came in a million parts and 5th gear fits both ways and only one is correct 

[PJM47]

Thanks really helpful advice. I’ve ordered those piston rings and will look for the right gasket set.
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..

[philward]

I know that the cost of the strip and find you have done is going up and up, but I always put the full cam chain train wheel/blade/etc as after almost 50 years, the material will be degraded - advice on here (which I have always taken) is use genuine Honda as after market stuff is of variable quality - plus upgraded DID chain from Julie. As for the primary chain, I always fit one - check the tensionar wheel for damage (once again 50 year old, blah, blah, blah!)
Bloody expensive these rebuilds

[Trigger]

primary  chains can be had at a good price, just not in this country. If you know anyone that does business trips to japan or is off on holiday to there but, can be pricy if you have them posted here >>> https://www.yamiya750.com/index.php?main_page=index&cPath=246_21_250_63

[royhall]

The good thing about the 750 engine is that nearly all the parts are readily available, but sometimes at a premium price.

[PJM47]

so most bits on order now (ouch).

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.

[Nurse Julie]

so most bits on order now (ouch).

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.

Honda Bond, 3 Bond , Yam Bond etc for crank case halves only. The lightest, lightest smear, so light, you can almost see through it.