my buddy has a 250 trailblazer and when its cold it starts right up but run it for awhile and it will crank and crank and either never start or start after minutes of cranking...it will not idle for more than 10 seconds so that rules out just leaving it running...i sprayed a halfa can of starter fluid in it and it didnt phase it a bit.

 

have you checked for spark, fuel in the cylinder , oil on the mag ?

 

yeah check the spark plug and see if it is any good .... or better yet put a new one in it and try it out ... I dont know but you might be running a little fat on your jetting ... you may have to lean it out a little bit if it wont idle ..Austin

 

also ,ive seen where gas tanks lock up do to bad caps. next time it does this try taking the cap off and see if it starts up. old metal gas tanks and caps are notorious for this.

 

I had a bad crank seal that had a similar effect.

 

Piston rings could be stuck it happened to mudmaster250. His wouldnt start after it was hot.

 

yes it did happen to me.. ... twice as a matter of fact. well u can go the cheap route and jsut re ring it or u can go the more expensive way and bore it and put in a wiseco(the better choice) and your friend might be able to get it porting and have the head milled while he does that like i did.

 

holy **** man your gonna blow that thing up with that much starter fluid. even a couple shots could blow it, that stuff lights so easily its not even funny. be very very very carefull with that stuff.

 

Check the compresion if it is under 100psi you need a rebuild.Bet you that is what it needs though.

 

Using a half of a can of starter fluid and it didn't fire, I would say it needs a rebuild! Like someone mentioned, check the compression. My 400 did the same thing.