Re-Jetting starting point

[dbart250]

I've searched and searched and yes, i know there are a lot of charts and temperatures, and altitudes, etc etc, but i know someone will have a good starting point. i have a slightly-bored out-after-seizing 91 yz250 with a fmf fatty/powercore aftermarket set up and will soon get new reed pedals. right now the main is 350, the rest of the carb is stock (pilot 45, needle 6dj8-61 4th position). i run 40:1, weekend warrior, in the cornfields of northern illinois. right now the plug is good color (clay). so before i chop plugs, should i grab jets at 355, 360 or should i expect a big jump with the new power reeds? thanks ahead of time.

[dbart250]

Ill add that i found fmf suggesting a 370 main, but thats at 32:1. Does it change a lot running 40:1? Or should i just change the premix?

[RCannon]

32:1 and 40:1 amounts to about whats left on the side of your ratio rite....no big deal at all.

For jetting, its usually always best to start with stock jets unless someone near you, running IDENTICAL oil and gas gives you their numbers. Even then its not much help since rider ability and preference play such a large part in jetting.

[FGR01]

32:1 and 40:1 amounts to about whats left on the side of your ratio rite....no big deal at all.

I never have any left on the ratio rite. I pour some of the gas in there and swish it around to get all of the oil. I've always figured that was the only way to get your mix ratio exact.

I can tell a difference in how my 125 and 250 run between 32:1 and 40:1. The bare pipes even get more blue on them further from the cylinder when running 32:1.