yzf426/wr400 question

hello, i recently put a 2002 yzf426 exhaust on my wr400. It has all those free mods you hear about. I was wondering what the carb jetting should be because it doesnt feel like its running right. i heard once that the 2000 wr400 had the same carb as an 2000 (possibly even other year) yzf426, so if figure since i practically have the same motor and all as a 400, and the 400 and 426have the same exhaust, that it should be the same or real close. In other words, whats the jetting for an early model 426? Thanks-ed

Yes, they are the same carburetor, but they are set up differently. You are probably running a bit lean now because of less restriction in the yz exhaust (that's why you bought it). It shouldn't be too far off though, have you adjusted your fuel screw at all? See how far out it is right now. If you haven't ever touched it, it's probably 1 5/8 turns. Richen that up in 1/8th turn increments (Probably not to exceed 2 1/2 turns out or so).

Here's the difference between WR carburation and that of a YZ:


Main Jet - 165; 162

Pilot Jet - 42; 42

Needle - 3(OBDRS); 4(OBEKR)

Fuel Screw - 1 5/8; 1 3/4

**NOTE: I am not telling you to set up your carburetor like the YZ because there are other factors that contribute to the reasoning behind how they are set-up. I just want you to have an idea in how they are different.**

I've never been super good at jetting, but some of the guys on here seem to have it to a pretty good science. You can also read the technical thread on jetting found [thread=2892998]HERE[/thread] and HERE. Good Luck!

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