if you run without the power valve you will have no top end. Did you buy this bike cheap or something recently? Dont just replace the piston and rings without doing the PV.
Just out of curiosity, which O-rings are you speaking of that leak? If your talking about the head then yeah, your bike may fire up for a second then die, your pulling coolant down into the bottom end and cutting out the spark.
Still confused on how you have a bike with the PV missing and never noticed it.
Maybe his is bored to 310. If you needed to shave it to go from 250 to 265, do you think you could go to 310 without removing it? BTW, his '95 also has a different motor than your '02.
I'm just throwing out ideas why someone would remove the powervalve in a dirt bike. Besides accomodating an over bore, the only other thing I can think of is the PV was worn out and busted, and they did want to spend the money to repair properly.
The poster said the 'bike seemed to run OK' even with a worn out top end and no PV. Would it run OK in this condition on a stock bore? Maybe not, but it could with a 310 kit.
so i bought powervalves for a 1995 rm 250 (since mine were missing) only to find out that my cylinder was from a 1992. i bought a new piston and waited a few months till i came across a cylinder with powervalves like new,a few hours but in great shape, so i got it all together ,after cleaning measuring and lubing, couldnt get it to start by kicking so i drained the gas put it where it could get warm then pull started it behind my three wheeler. i had to put it in third to get it to turn over. its got the most compression ive ever seen. igot it started but only ran it for a while . when i mixed the gas out in the cold it was like a wad of molasas? thats why i warmed the gas first( heated porch, not blow torch) im gonna do a compression test when shes broke in . form what i could tell its a completely different bike. kansas weather sucks.
Well normal gas won't thicken when its cold out. Even gas mixed with oil should not be noticeably thicker when cold. I would say you have bad gas or oil. I would go pickup brand new gas, and mix in some good 2T oil.
Also, if this thing is freshly rebuilt and put back together correctly it should fire right up. If you have to tow it behind something to get it to start, that indicates there is probably something wrong still. Trying to start it like this will only make the problem worse.