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My brothers bike would stall deccelerating around a corner or going down a hill during a hare scramble this weekend. He says his bike stalled a lot out in the woods. Besides the stalling it ran real good. I work on his bike so I'm just wondering if his pilot circuit is too lean or if his float height is set wrong. The way he described the stalling I'm wondering if the carb isn't getting enough fuel fast enough to feed the pilot circuit .

Any suggestions would be helpful, thanks.

04 CRF 250R

was there any carb work done recently? any other work that may have introduced this condition?

ken

No carb work. There was new piston rings and valve seals put in, and also a clean air filter. I went tearing down a dirt road to break it in a week before the race, it ran awesome. No stalling. Then the next time the bike was ran was at the hare scramble.

was it sitting for a while without being started?

The longest it sat without being started was a week. The day I test rode it for break in, it was about 50 to 60 degrees. And the day of the race it was 30 to 38 degrees.

so since it wasn't sitting for some time it's likely not junk in the float, sticky float set or clogged pilot jet. it wouldn't hurt to verify these however.

that said, if the jetting was spot on before you may need to reply your floating valve seal on the slide.

also, while you are into the carb check your accelerator pump diaphragm. these are known to deteriorate over time.

What if the hot start got partially stuck open or all the way open ?

yes that would do it. the hot start leans out the mixture so if it's stuck open...un-stuck it.

GRLSRFN wrote:The longest it sat without being started was a week. The day I test rode it for break in, it was about 50 to 60 degrees. And the day of the race it was 30 to 38 degrees.

I think you just answered your own question. It was most likely too lean at the low temp. Try going up 1 size on your pilot jet when its that cold.