valves stuck?

[ridinghard]

Long story short I just found all cylinders have about 120 PSI until it runs for a bit, then cyl 2 drops to about 60 - 90 PSI.
Would pouring Marvin mystery oil in the spark plug hole help things from sticking? Is it the valve sticking or is it something else? When it sits for half an hour or more it has full compression again. I think cyl 3 looses compression at start up sometimes. I couldn't recreate it tonight and check the compression but last night cyl 3 exhaust was colder than the others for the first 10 minutes of running. It sputtered a bit out of that exhaust too. Then it stopped sputtering and that cyl exhaust was as hot as the rest until about 20 minutes when cyl 2 sputtered and was colder.

I just got the bike a few months ago and it had sat for over a year according to the guy I bought it from. He did drive it once or twice last summer but that is it.

[Ivan]

Check your valve clearance.

As valves wear, the seat and valve deteriorate, and that lets the valve sit shallower in the head.

As the engine warms up, the valves elongate from heat expansion. When the clearances are tight already, this causes the valves to stay open at teh base circle of the cam. This results in no compression, backfiring and general crappy running, until the valve cools down and shrinks again.

Left untreated, it can eventually cause burnt valves, but that is if you keep running it with the hot misfire.

[bikerphil]

Rings might be stuck if the bike was sitting. MMO will help them free up. Check your valve clearances to eliminate that. These valves don't really stick as they are not hydraulic. Sounds like the carbs need going thru also. They will gum up in a hurry if not used enough. Try some Seafoam gas treatment before taking the carbs apart.

[andreashweiss]

cylinders/pistons

If needed, I have several used pistons and rings, plenty of life left in them, also have 2 complete cylinder heads that came off running bikes, spare cams, etc, just send me a private message if you need anything, thanx andreas

[ridinghard]

I'll remember the parts if need be. I'm thinking of going to performance parts as I need to replace anything.
I'll dig into it this weekend and see what I need.
I have already cleaned the carbs over 8 times while trouble shooting this. As well as redcoat the tank, and changed all lines and the ignition coils.