I have a 1990 Polaris Trail Boss 250. Will start and run fine when cold. No noticable issues. After I shut it down, it will not restart until it cools. Plug is firing. Compression on cold engine is about 105psi. Any ideas?

 

I know it may sound stupid but check your battery connections and see if there on right. Could be it starts then the vibrations rattle you connections loose then you let it cool down but when you get on it it reconnects? XD

 

Actually bought a new battery tonight. Still have problem.

 

I meant wires leading to the battery.

 

maybe your valves need an adjustment. i can't imagine you going through a vapor lock scenario. but then again, you didn't state how long you run the quad before it won't start up warm. normal operating temps?

 

Checked battery cables terminals and connections. All clean and tight. I do get atv up to normal operating temp. This is a 2 stroke. Does it have valves that can be adjusted.