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jetting '01 CR250 PWK Jetting

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I've been doing quite a bit of reading on the subject but just looking for more insight on my particular setup:

I have an 01 CR250 with a 38mm Air Striker from JD Jetting. It currently has the factory(JD) jetting in it: #7 slide, 45 pilot, 175 main, blue needle on #3, air screw 1.5-2 turns out. The bike has a fresh top end(did it when I installed the carb), Boyesen carbon fiber reeds, FMF Gnarly pipe, and a fresh-packed FMF Shorty silencer.

The idle/pilot seems to be pretty close, although it may be a bit rich. I've noticed the air screw doesn't seem to have much affect when adjusting it.  The other issue I've noticed is a slight bog when I get on it at lower speeds/RPMs. IE: Making a slow, tight turn in first gear and then getting on the throttle coming out of the turn. There's no sputtering/etc, just a bog/hesitation.

I'm assuming the needle will play a big part in fixing this, but does this indicate a rich or lean condition?

Also, I'm setting this bike up for single-track/enduro/woods riding. Any advice on jetting/needle combos that'll give me the cleaner part-throttle/low RPM response I'm looking for?


Edit: My altitude is around 600-700 above sea level(Chicagoland) and the current temps are in the 60s-70s.

Edited by D.Barrett

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The needle effects the entire rpm range, as well the slide cutaway and if there is a notch or not. A higher slide number gives you leaner conditions and vice versa. Richer conditions provide more low/mid range torque.  Throttle response increases when the airscrew is turned in. Pilot jet controls idle, but still delivers fuel throughout the entire range.

I’ve got a similar set up like yours (99 engine + airstriker). However, on the search for leaner conditions i experienced a low end loss in torque with the JD needles (red/blue, 4th – 2nd clips). From what I reed in forums the JD needles seem to work better on case reed engines with airstriker carbs. There are a bunch of needles that might be worth a try (Yamaha, Suzuki, 99 and 00 CR stock). But before I suggest to go through the testing sequence, that is outlined by JD.

Currently I run the 99 stock needle and #5.5 slide w/ notch again, 45 pilot, 178 main, 98 RON ethanol free pump, 1100ft, temps in 60s - 80s. Bike runs great. Even with a PC pipe I got decent low/mid torque, but there is still some spooge around the silencer, so next I’m about to try 42/172. Hence that a #5.5 cutaway is already a little richer than your #7.

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