Broke a ringland and just replace it with a new piston with new rings. Installed everything and the compression was still giving me 120. compression test is 120/250/245/250. I'm guessing the valve seal? can a valve seal lower your compression? hopefully its not the valve. any help will be great. Also there is smoke coming from the breather. theres no oil leak or anything.

 

more info.

what's the mileage? was the cylinder rehoned? did you do the repair or did a shop do it?

since you're asking about the valve seal, i'm assuming you didn't check, or have it checked while the head was off. a leak-down test may tell you more than compression in this case.

 

yes leakdown's will help pinpoint where you're losing compression. valve seal do lower compression to answer your question.

 

yes... good call.

valve seats on the other hand can lower compression

 

my mistake. I must have misread about it before. I've always wondered to myself 'how would a bad valve seal lower compression?' A valve seat makes much more sense. Thanks for correcting me.