Help w/ YZ426F Acceleration?

Hey Everyone,

So I recently bought a dyno jetting kit for my 01 YZ426F. The power isn't bad but I know it's not the most it could be. I'm currently running a 42 pilot, 170 main, and dyno needle on the 3rd clip from the top. I live in Phoenix, AZ and the elevation is around 1100 ft w/ a temp of 70-110 degrees. I have so bogging issues when I quickly get on the throttle (that first 1/8 or so) which I've heard the BK mod will fix. Does anyone think changing the needle position to maybe the 4th clip from the top will give me a little more power from 1/4 to 1/2 throttle?

Also, I'm running a DR D full exhaust w/ an aftermarket air filter..


The Dyno Jet kits are garbage. Get a JD jet kit and wire up your accelerator pump. It will feel like a rocket!

Don't waste money on a jet kit. Jet kits aren't calibrited for your specific elevation, mods, and temps. Every jetting question you may have can be answered here.

Try a 45 pilot and 165 main and go from there. What is your fuel screw set at? I'm sure someone on here can give more precise jetting.

My fuel screw is 3.5 out so I definitelt need a 45 pilot

I have an 02 YZ426 with a full Yosh system. In SW Ohio (in summer), i see 80-100F temps and I am at 900' above MSL: I am running a 45 pilot and a 165 main, stock needle in the 4th position. Fuel screw hovers around 1.75-2.0 turns, depending on humidity and how old my gasoline happens to be. I have not done the BK mod. Haven't felt the "need".

Your 170 main sounds too fat. Pilot will likely be OK. Big gains can be had by playing with the needle. Too bad it is the hardest part to access.

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