Engine reconditioning - any specialists about

[Warthog1959]

Hi just bought a tatty 1978 CB750 1978. Can any body out there recommend a good specialist for cleaning, reboring, porting rebuilding etc. Preferably in the Norhamptonshire area, but will travel if necessary. Can't do it my self or I'll be at it for the next 10 years.

[mick]

Hi you could try John wyatt at rising sun restorations , cheers Mick.

[Andy1976]

I've been recommended John Wyatt too, He's got a unit near Wetherby. His number is 01423 358004.
Also there is Jim Morley at JME Engineering, 07984 388405, He did my re-bore a while back, based in conningsby, Lincs.
Red rose retrobikes in Toddmorden, Lancs, 01706 839278.
http://www.redrose-retrobikes.co.uk/

Cheers
Andy

[Bryanj]

At 78 it should be an F2 and they have known problems with exhaust valves and guides plus original parts like pistons are different and not easy to come by.
Dynoman in the US does overbore kits and replacement valve/guide kits but i dont know of anybody in uk

[hector2800]

Jim Morley has moved in to Boston recently but his number should still be the same.

[Yoshi823]

The 750 engine is one of the easiest engines to work on.

I recommend new valve guides made from aluminium/bronze to the standard lengths.Too short and the valves 'wobble' and cause back-to-front bore wear.

I also suggest that whenever anyone has an engine out of the frame to replace the tacho drive oil seal.When this leaks there is nothing that can be done except having the complete engine out...just for this very small seal.

I heard that the pistons and rings to use are the CB350 twin items.I think this takes them out to 65mm bore size and 836cc with a standard stroke....but don't quote me on this as I remember reading this a fair few years ago.

[Seamus]

Just for info the CB350 pistons give a volume of 810cc.

How do I know? Cos I have one. Be aware that the compression is also increased a good bit as the CB 350 pistons have a bigger dome (as opposed to the flat pistons of the 750).

[SteveD CB500K0]

There are a couple of very good independants around here (Reading) who will work on these old bikes (they actually prefer it)

Let me know if you are still looking.

Steve

[mick]

Hi it is possible to replace the rev counter drive oil seal with the engine in the frame  cheers Mick.

[Seamus]

It's not supposd to be, but if it is fitted from the outside it could be possible to hook the old one out and replace.

Unfortunately I cannot remember as I did mine with the rocker cover off.

Best advice is have a look and see if you can get it out.

Good luck

Seamus

[Yoshi823]

Hi it is possible to replace the rev counter drive oil seal with the engine in the frame  cheers Mick.

Mine did need doing and I was really annoyed that it was not possible to do it in any other way other than to remove the engine.Hence the frame mod that I made.Photos to follow once downloaded onto photobucket.

[mick]

you CAN replace the seal WITHOUT taking the engine out ,use a small self tapping screw,  screw it into the old seal take care not to damage any of the alloy seat,  grip the screw with pliers and pull it out, slide the new seal over the shaft and use a deep socket of the right size and some lube and tap it into place job done  works ok for me  cheers Mick.

[Yoshi823]

If only I had known this when the job needed doing back in 1979.

But they didn't have the internet back then.