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Klx300/tm33 Jetting

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Note: I posted this earlier on the KLX forum. Any input would be appreciated. My theory may be not very sound due to my limited experience in this field.

Earlier this year I purchases a Mikuni TM33 pumper carb kit from White Bros. I installed it on the bike ('04 KLX 300, free mods, WB header, Twin Air filter) as it came set up from WB. Here's how it ran:

1. Off idle to 1/2 throttle, O.k.

2. Past 3/4 throttle to WOT, stumbling rich. Main Jet obviously too big (rich). would not rev out on top end. Plug black.

3. Releasing throttle caused major stumble, and I mean major. Vertict- needle too high (rich).

Moved needle clip to second from end position. Went for ride. 1/4 to 3/4 throttle hit now better. Less stumble upon releasing throttle, but still there.

Moved needle to end position (leanest). Remove MJ. MJ was 145. Installed 140 MJ, which is the smallest supplied with kit. Went for ride. Here's how it ran:

1. Idle to about 1/4-1/3 throttle- flat response with a little hesitation. (lean)

2. 1/4 - 3/4 throttle- Much better. Slight stumble on throttle closure.

3. WOT- Still a slight hesitation, but will now clean up and make some actual power.

One more move on the main jet (thinking like a 135) and that should be set up good. As far as the needle is concerned, and this is where I would appreciate some feedback from those of you "in the know" is that I need to install a smaller needle jet. This should allow me to raise the needle up a bit to where the taper will be out of the needle jet sufficiently to fatten up the 1/4 throttle range, and be leaner to eliminate the stumble on throttle closure.

I think I (may) have it figured out, but any feedback would be appreciated. Thanks!

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