cylinder not firing when hot

[Fireroad Express]

bike starts fine and idles well but when i take it for a warm up run it drops a cylinder with in half a mile when it comes up to operating temperature. anyone got any thoughts on this?

[06specialedition]

Have you tried new plugs?? Mine was doing that and new plugs made it run perfect.

[Fireroad Express]

i tried several sets of plugs so far.

[matt1]

Does it completely drop the cylinder or just at idle? I had a problem with dropping a cylinder at idle after a few minutes of riding once and it turned out to be a slide problem. The pin that aligns the slide in the bore would allow the slide to turn, after I hit a few bumps the slide would turn and drop the cylinder at idle.

Edited July 30, 2010 by matt1

[Fireroad Express]

Does it completely drop the cylinder or just at idle? I had a problem with dropping a cylinder at idle after a few minutes of riding once and it turned out to be a slide problem. The pin that aligns the slide in the bore would allow the slide to turn, after I hit a few bumps the slide would turn and drop the cylinder at idle.

 

the problem happens to mine when it heats up. i"ll go for a short warm up on a trail behind the house but when i take the bike down on the road and hold the throttle open and go through the gears thats when it drops the cylinder and starts to bog out.

[pr0blumz]

Sounds like an electrical problem.

[bigborebanshee]

Does it drop the same side?

 

have you tried switching your spark plug wires?

 

Swapping out reed cages?

 

Or a leak crankcase leak down when its warmed up?

 

I would put my money on an air leak,probably crank seal.I just rebuilt a CR250 that was doing the same thing.kept thinking it was the jetting.