jetting and airbox help

matthew patton pattonme at
Tue Aug 24 06:17:08 PDT 2010

I finally got the front carb to stop dripping raw fuel down the carb throat. somehow replacing the float needle and it's brass fitting and the float did the job. Not sure why but I'll take it.

I've got 17.5 pilots, 150'ish mains (I think) and aftermarket needles (not dynojet, name escapes me) at clip 4 from top, BMC air filter and Yosh race can.

I've been trying various things and can't seem to make any decent progress. What is a good starting point?

How much jetting difference should it make with open airbox vs BMC? 1 needle clip? 2?

Without the BMC it runs a little stutter at >1/2 throttle and 6000 RPM till about 7.5K and then it cleans up and seems to pull reasonably strong to 9K. With the BMC in it gets massively ragged at 6K and anything past 1/8 throttle and never cleans up.

I'm guessing my BMC is clogging up the airflow (I'll clean it again) and I'm jetted way too rich for the BMC but ???? for open airbox.

Can anyone clue me in?


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