Compression goes DOWN when hot...

[viggen]

Well, finished my valve adjustment and the LH EX was pretty tight.  Went from a 2.75 to a 2.55 and now I have a gap of ~.102, so nice and loose.

Did a cold compression check, and the LH cylinder is only @105psi.  RH is ~130.  Put oil in the LH cylinder and the compression jumped up quite high... ~150psi. 

Ran the bike, it runs ok.. A little rough at idle but I always assumed that was just a GS thing.. Did a hot compression test and the LH cylinder was down to ~90psi.  RH was up to 150psi. 

I'm thinking that if I run it hot enough, I'm going to see the same stalling problems... Just wondering if anyone had seen compression that went down when hot?

Gonna get everything back together this weekend and take her for a spin.  Would like to put another couple thousand miles on before the end of the season, and do rings this winter if I can get away with it.  Unreasonable? 

[burning1]

I would expect compression to drop when hot if your valves are extremely tight, but since you just performed a valve adjustment, I don't know what to say.

It sounds like a leakdown test is your best option.

[pandymai]

if the valves are ok and sealing properly, i would imagine youre lookin at blown piston rings.

+1 on the leakdown test

[the mole]

You've gone from 2.75 to 2.55 and have .102 clearance? So does that mean you must have had negative .998 before?
I'm guessing that if your LH exhaust was that tight you've got erosion on the valve/seat and you need to get the seat cut and maybe a new valve. Time to pull the head.