Won't start when warm

My bike starts fine when it's cold. Plenty of juice, and lights are nice and bright. After it has warmed up, the starter can just barely turn the engine over. Sometimes it will start, but more often not. The lights are still nice and bright. After it cools off, it starts fine again. I know I should probably go through the whole charging system and test all the components, but I was wondering if anyone might have run into this or have an easy solution.

Thanks, Dan

I would first check the voltage to the starter when it is cold then check the voltage after you have warmed it up. But I would say it does not sound like a wiring problem, more likely it is in the starter itself so it may just need replaced

Another thing to check is your timing advancer. Mine had stuck in the advance position and caused that exact problem. It also knocked under hard acceleration, but it would barely turn over when the engine was warm. I fixed it and it fires right up now all the time.

How 'warm' does it get? Could it be a compression problem?

When the engine heats up it would expand a bit, and without the needed compression you could have one helluva time starting it.

The part about 'after it cools off, it starts fine again' leads me to this conclusion based on something my father told me about his old '68 (I think) triumph - he'd have the same trouble on long hauls.

Thanks for the suggestions...

I replaced the battery, and it seems to be fine now. The old battery had no acid left in it and the terminals were corroded. I guess I'll have to wait to see if this a permanant fix, but for right now it's working great.

i had the very same problem, cleaned up the battery connections and she is like new.