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Jetting the 426


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This past weekend I changed my jetting for the first time. My 426 had the stock jetting which wasn't that much off but did need some fine tuning. I went with the recommendations I got off of the website http://www.strokerspeed.com. They recommended going to 48 pilot and 165 main, with the fuel screw 2 turns out. I'm in NM at about 4000 feet and they said these specs were good to about 5000 feet. Anyway just letting you know that these specs seem to be spot on after testing.

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The 426 has completely different jetting with the new carb, and it can't be compared to the old carb.

Scott F

Originally posted by Chris in the Mojave:

Wow, that main jet sound surprisingly lean. What was the Stock main jet? In the 400 it's a 175 and I ended up with a 180 in it with my FMF PC IV, stock head pipe @ 2500 ft. I forget how many turns out, I think it was 2.75.

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Scott F

'00 YZ426F

'99 YZ400F sold

'98 YZ400F sold

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Scott is right, the new carb is different. The stock setting were a 162 main and a 42 pilot. Mine was lean on the bottom and would pop on deceleration. It wasn't too far off with the stock setting so it took me a while to learn that it needed some fine tuning. With the setup I have now it no longer pops and seems just right.

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