valve seating giving me no compression?

hey all,
just picked up a non running 82 kz750 ltd....i knew it would need carb work and that was all. after doing a compression test i found no compression unless i put my hand over the carb i could get a little. the cylinders seem smooth/clean, the pistons look decent and the piston rings also seem ok. what i'm thinking is that whoever had it before me tried to do carb work on it but did not sync them after. which caused carbon build up on the valves so that they do not seat properly.this would go along with the fact that i could get compression if i cover the carb. i'm far from a mechanic which is why i have this project but i'm wondering if this makes sense? when the valves are closed should they be sitting flush with the face? any help or guesses of what to check would be awesome.

thanks,

kyle

Either your valves are not seating tight or the camshaft timing is wrong. You should check valve clearance.

if the valves aren't sitting flush with the seats then it sounds to me like you have some bent valves carb sync would in no way cause the problem your talking about it either has had the cam's installed incorrectly and they have made contact with each other or with the pistons or the timing chain has jumped somehow. or a tensioner has broken or worn out badly enough to cause excess play in the cam chain causing it to jump that would be a very extreme case but it could be possible.

kylevk wrote:

hey all,
carbon build up on the valves so that they do not seat properly.

On my 750, when the valve guide seals go bad, the oil trailing down coats the seats and the oil residue burns on and (over time) keeps them from closing fully.

i dont think its bent valves, they sit flat, but theres a lot of build up so its possible that they might not get a good seal.

I have seen a lot of build up on valves over the years but it never stops them from seating, if you have the head off, pour some light fluid like slovent in the ports with the valves closed ( head standing on side ) if the slovent runs out, they are not seating and will need to come out to see what is wrong