06 Yamaha 250F Jetting Sea Level

I have been reading through all the threads about jetting on a stock 06 YZ250F, seems like many people recommend 40/50 LJ, 45 Pilot, 1 1/2 turns on FS, Stock needle 4th position, and a 170 main. I can see richening up the low end, it seems lean stock off idle to about half throttle, I just wanted to know if anyone is running the 170 main in colder temps (40-50F) at sea level? Seems like a drastic drop from the 178 main stock and I wanted to hear some real world experiences before giving it a try.


33 views and no one has tried different setups at sea level yet?

i would say if your in doubt to leave the stock 178 main jet and do the rest of the set up.you can always lean the main jet a step at a time as your testing.

I haven't read any set-up jd jetting for the 250f but, 4th clip 170 main is what I run on the 450, the 250 stock main is 178, I cant see going down to 170 on a 250. I just re-read the dirtrider article on 250f shoot out and they rec. stock jetting for mx on their test (at sea-level)

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