YZ250 Carb, jetting and weather condition

[Jarda]

Hello
I'm looking for help with proper carb setting, proper jetting in different weather condition. How can I find (calculate) proper jet in cold, warm or wet weather? What should be a needle position and fuel/air mix screw position? Is there some table for YZ250 '00? My previous ride was perfect (cold, rainy), yesterday was slow acceleration (cold, dry weather). Any tips?

Thnx
Jarda

 

[biglou]

General rule of thumb, the three H's will cause you to have to lean out the jetting: Height, Heat and Humidity. The more of any of those you get, the leaner to jet. The less of those you have, the richer. SOunds like the change in your weather would have called for richer jetting. Just how much, I can't say exactly. Hope this helps.

 

[bclapham]

i dont think you need to change the power jet. I have the 01 with the NE3J needle in the second from top. I leaned the needle but the bike ran funny (i do have to recheck this though). so i have the needle in stock (2nd clip) a 45 pilot and a 175 main. BUT, be careful, i am in hot so cal and at altitute, if you run these settings on a cooler day you have a good chance of siezing!