Need help with jetting.

I have a 2000 YZ 426 with a Pro Circuit T-4. I just put the pipe on and it runs like crap. Popping very bad. I called Pro Circuit and they said they didnt have any books on the jetting for my bike. Cna anyone please steer me in the right direction? Thanks

I am assuming it was running great with the stock pipe? Does it pop under acceleration or deceleration or both? Does pulling the choke help? Usually if the pipe actually increases power, you will need more fuel. Tell us where in the power it is acting up (low, med or high throttle)? Does it start well? Have you changed fuels? Is it alot colder where you are all of a sudden?

Dude try a 160 main, stk pilot jet, fuel screw 2 turns out, needle 3 nothch from the top. :cry:

Ok here goes. I had a DSp pipe on it. 172 main and I believe 46 pilot. Ran great. Switched to the T-4 and it starts ok but doesnt idle well and pops like mad decelerating. Wants to die when I come to a stop. Thank you guys for your help.

turn the fuel screw out a 1/4 turn and see if it helps. Also check that the float works correctly.

Read this article to understand a little more about jetting then try setting your fuel screw the way they describe in the article.

If mine were that lean, I'd see what jets were in it and go up one level on the pilot and main and see how it runs from there.

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