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James! Need jetting Help!

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Hey James,

I just tried your recommended WR 400 jetting and my bike has a sumble at partial throttle (about 1/4 to 1/2). Here is what I tried:

165 Main

48 pilot

EKN needle in 4th position

1 turn then 1.5 turns out on the air screw.

My bike is a '00 model; stock exhaust with Vor tip; YZ timing, grey wire mod.

My jetting before was 170 main, 45 pilot, 1.75 turns out on air screw.

I did the WZ timing and grey wire mod, and experienced the similar hesitation (about 1/4 throttle).

I did not have the hesitation before the YZ timing and grey wire mod.

I ride at 1,000 to 3000 feet elevation.

Think I should try going back to the 45 pilot or dropping the needle?

Sorry about posting a reply about this in your other "conversation".

Your help will be appreciated.


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Have you considered the BK mod? I found that after changing my jetting I still have a hesitation just off the bottom. By adjusting the timing of the squirt and the duration, I was able to eliminate the hesitation. For my 4500 ft location the #48 was a little rich all the way down to 1/4 turn out on the fuel screw.


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1.5 turns out is too much with a #48 pilot jet. Did you get the #100 pilot air jet? Expect 3/4-1 1/4 turns out on the pilot screw with the #100/#48.

With a stock pilot air #75 use the #45 pilot jet and 1.75 turns. Dropping the needle by using the #3 clip is also a good idea for a next step.

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