Hi everyone,

I recently purchased a 1990 Trail Boss 250. It needed a bit of work, but overall, was in very good condition.

I replaced the starter on the machine. I have also replaced the clutch cover, and installed a new battery.

When I first got the machine, I got it started, and ran it on a limitted basis (no clutch cover). I never had a problem starting the machine cold or warm with the pull start.

Since replacing the starter, the machine will start beautifully when cold. Once it has been run for a while, and shut off, it will not start warm. I checked the spark, and it has no spark when warm. If I let it set for a while, and come back to it, it will start right up again.

I don't know if the starter being replaced is coincidental, or has anything to do with it. I am betting it is coincidental.

I have evaluated the ETC, and have by-passed it temporarily for the purpose of troubleshooting. I origionally suspected the kill switch on the handlebar, thinking it was just intermittant, and not related to the machine being warm. I disassembled the handlebar switch, and checked the contacts for continuity. When the kill switch is activated, it completes a circuit (I assume this circuit is to ground).

It continued to do it today. Let it set for a while, and it will fire right up quick, and run beautifully. No misfires, no problems (idle is a bit low, but unrealated). Run it until it is warm, shut it off, and she will turn over and over, with no start.

I do not have a service manual for this machine (this will be my next purchase). Something in my mind leads me to the coil. It seems that I remember my father working on a snomobile that would not fire when warm, and that was the issue (although it fires fine when running... just won't start.)

Does anyone here have any input? Thanks!

 

are u sure there is no spark when warm? ( check it in a darker area with the
spark plug touching the head making a good ground or use a spark checker)
if u don't have spark it sounds like it is all heat related. most likely the coil,
the cdi modlue, or the stator(cdi trigger coil) the service manual will give u
all the resistance values of these, also will it start if u pull start it when warm?
if it does then something in the starting circuit is messing it up.

 

My boys tb 250 wouldnt start when warm. It turned out to be low compression.

 

Low Compression would explain it if it were firing, but it has no spark when warm.

I have not checked for fire/start with the pull start... maybe I will get a minute to do that tonight.

If anyone else has any input, I would be appreciative... otherwise, I will begin to troubleshoot with the coil once I check to see if it has any spark with the handcrank when warm (although that would be really confusing!)