I have a 1992 Seca II that won't run. I always thought it was something to do with the carburetors since the previous owner had put in different size main jets (not all of them the same size) and the synchronization seemed way off (based on the bench method of synchronizing them), so I took them off, made sure they were reasonably clean and none of the jets or passages were clogged, and set everything at a kind of nominal setting to see if I could get the bike running and then tune from there. I also put the factory size main jets back in. The bike had individual pods filters and an aftermarket header and exhaust, so I put a factory airbox on it but left the aftermarket exhaust.
The bike comes close to running, but it clearly isn't firing on cylinder #3. The header pipe on 1, 2, and 4 get hot but 3 stays cool. I know the valves are good from recent head work, and I've checked all the valve clearances. What I'm down to is that I've done a compression check, and 1, 2, and 4 are around 140, and 3 is 130 or so when the engine is cool. If I squirt some oil into cylinder #3, the compression jumps to about 150.
I guess my question is, is it likely that the low compression is likely why the bike won't run, both from the standpoint that 3 isn't firing and also the effect this non-firing cylinder has on the others as far as carb balance is concerned?
I have a feeling the odd carburetor settings I found were how the previous owner could get it to at least run, even if poorly, and maybe this cylinder has been an issue for some time.
