Topic: CB400F valve stem seals and timing chain.

[rustyrescue]

The bike sounds and runs like a different machine having set it all up.

I had one some years ago, made a cam chain adjusting bolt to use from the top plug. Currently adjusted using the book method it has a very light tinkling sound at idle speed. Nice and quiet otherwise, does this sound acceptable?

Also it is clear and smoke free until really warmed up, then it is a bit smoky after idling or low revs then opened up.

Good compression, has been sat many years and I do not believe it has had stem seals in the past so they are good and old! Has anybody done them with head in situ? rope in cylinder or the like and if so what was used to compress the springs?

[awrawr]

Tried rope once years ago. Miserable failure. Did the valve seals recently (well old) huge improvement in exhaust smoke. (From loads to none). Well worth the effort and a new head gasket.

[Tim2005]

I've replaced valve springs with the head in situ, about 15 years back when I broke some overrevving it. I just made up a suitable piece of metal as a lever to push the retainers down with, and brought the appropriate piston to tdc so the valve rested on it. All done very carefully of course, but worked fine and only took an evening. 

[rustyrescue]

Thanks Tim, that sounds promising. I put 40 odd miles on the bike at the weekend, it runs nice and smoke has improved having run it a bit since many years of storage. It does still smoke too much though at higher revs when opened up a bit and also after idling for a bit. Its quite blue smoke but I do suspect stem seals still.
If you managed it resting the valves on piston tops I guess if I slip in a little soft rope and then raise the piston it will be safer.
Did you find enough room leaving camshaft in place and just removing the rockers/shafts with the top cover?
I would like to do the valve stem seals alon..leaving the engine untouched becasue if it gets to taking the head off then I may as well check bores/rings etc.

[Bodi]

You have free access to the valves if the rocker cover is removed... except for the frame if you don't remove the engine.
I made a spark plug to airline adapter to pressurize a cylinder and hold the valves out, with 90psi in there the valves hold in quite firmly. Pistons go to BDC with a lot force and speed if you pressurize it at exactly TDC and then nudge the cam or crank (ouch)... don't. You get to hear where it leaks as a bonus.
It won't be easy compressing the springs in frame, the claw type spring compressor I have wouldn't fit in there easily - it's a bugger to use even with head off... a clamp type is much preferable but they need the head off.
Note that only intake guides - the hardest to get at in frame - have seals. Don't find that out after struggling to get an exhaust valve spring off. Exhaust guides are different and will not take a seal.

[rustyrescue]

Thanks, I will have a go a little later in the year. I feel sure with fiddling and taking the coils off I should be able to get to the inlet valves.
I may go for the rope in bore route....I was working on a car many years ago and the airline popped off