SOHC.co.uk Forums > CB750

Crankcase seal leaking

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paul G:

--- Quote from: Trigger on October 26, 2017, 05:05:13 PM ---Just for Paul Gledhill >>>>https://www.youtube.com/watch?v=tRsm2G7bulI

--- End quote ---

Not my favoriye episode  ;) ;)

MrDavo:
If you really can’t be arsed to do a full strip down you could take the motor out, turn it upside down and undo the bottom case. You’d have to remove anything that attaches to both, I can only think of the ignition, clutch / alternator covers and gear change mechanism.

You could then lift the end of the crank to slip the old seal off and the new one on. Assembly is the reverse of disassembly, as Mr Haynes would say. The cases use sealant so getting a gasket in there isn’t an issue.

The are other seals you could / should change while you are there such as the final drive seal, but this looks like the minimum work route, the sort of thing I used to see going on in race paddocks when working to a deadline. There are potentially disastrous pitfalls such as the cam chain moving a tooth so you’d have to be careful there.

Others may be along soon in a state of shock to tell you why this wouldn’t work, it certainly isn’t the best way, but I am good at spotting a short cut.

Tomb:
I know lads who've used that method but not even gone as far removing the engine from the frame, albeit not on CB750's, but on other Jap fours.

I'd still have a go at doing it with the engine in one piece first, as said, what's there to lose, just be careful to not damage the crank. After all you have documented evidence of it working (posted by Rob 62)

Spitfire:
I always used to use the upside down engine route when working on CB750 gearboxes, why strip the top end when there is no need, just remove the side covers, gear change mechanism etc off and take the bottom crankcase off. Saves a load of work and hassle.

Cheers

Dennis

Blasta:
Yes, I'd spoken to a few people and was going to do the upside down thing if required.......but I don't think it is.

I had another go at the seal and it actually came out fairly easily and I managed not to damage anything.

The new seal was a nice snug fit and I put a little sealant around the edge. [ Guests cannot view attachments ]

Looks pretty good to me and I'm pretty confident it's not going to leak (famous last words  :) ).

I've got a few other things to do to it before it's back on the road, but I let you know if it's worked when I get a few kms on it.

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