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New Jetting for Lowered Squish Band

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This is a repost from the YZ Section.

I recently had my stock '05 YZ250 head done by RB Designs. He lowered the squish band to run on premium pump fuel. The mod was a great improvement in the way the engine ran. The motor sings now like a super clean running 125.

Since the mod, the spark plug is showing even richer than the "normal" wet YZ plug (??). I feel I need to lean the jetting out somewhere but the bike runs great and I cannot figure out where the motor is running rich. I will admit I am too lazy to spend half a day (a whole day for me) running the bike and pulling plugs on the trail, blah, blah.

I found a great thread here on how to jet properly, and I will do that if need be. But, if the fix is easy I'd rather keep the day and make the fix.

If anyone has a similar set up, or has some applicable jetting advice for the situation, I would surely appreciate it.

Senior A Rider, Harescrambles, Cross Country, Enduro

Single track to wide open fire trails at Hollister Hills and other parts of CA.

Stock: carb, jetting, cylinder, pipe

squish band lowered to still run on pump gas

filter skins on stock, and Uni air filter, Belray filter oil from bottle

FMF Turbine 2

91 Pump gas, Golden Spectro at 40:1, 1/2 ounce of octane boost per gallon

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