Crf88 tuning question

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Crf88 tuning question

This is a discussion on Crf88 tuning question within the CRF50 forums, part of the General Talk category; I've got the tb 88 with race head the 20mm carb it came with and I can't get it tuned I put a 38 pilot ...

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Thread: Crf88 tuning question

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    Crf88 tuning question

    I've got the tb 88 with race head the 20mm carb it came with and I can't get it tuned I put a 38 pilot and a 92 main jet in it the needle is second clip from bottom and my carb runs best at 3/4 turns out on the air screw and 4 turns out on the idle I'm from St Louis any help would be greatly appreciated

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    I think the 92 main is too rich in most cases, drop down to the 90 or smaller even. Also, run a bigger pilot, the 3/4 turns out on your air screw indicates that your pilot is a little lean.

    I have the same set up on a race head kit I just installed. I'm at sea level and I almost got the little bastard running right, 42 pilot with the screw 1.5 turns out. I've tried just about every main jet I have and seemed to have the best luck from 87~92, the 87 ran the best I think but it still coughs in the middle. I think this carb is just too big and too chinese. It would probably work better with the increased signal from a stroker crank, I ordered a PZ16 today in the hopes that it jets easier.

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    That TB20mm is a great carb. Tunes easy every time. 38 pilot and a 89/90 main at the most. Airscrew will be no more than 1.5 turns out.
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    Quote Originally Posted by RAZZO View Post
    That TB20mm is a great carb. Tunes easy every time. 38 pilot and a 89/90 main at the most. Airscrew will be no more than 1.5 turns out.
    What's your suggestion for same carb on 117cc?

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    Quote Originally Posted by tblumer View Post
    What's your suggestion for same carb on 117cc?
    I'm about 100' above sea level here. 108-117 - 38 pilot/90-92 main. Anybody that thinks those TB20mm carbs are bad can't tune a carb. Dial them in and ride.
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    ^ This is good to hear. I've been tuning carbs on two stroke motocross bikes for years but I've really been struggling with this PZ20. On most carbs I've dealt with being less than two turns out on the air screw usually indicates a lean pilot jet, now with this PZ I am only being 1.5 turns out with the 42 pilot I figured it was still too lean; easy cold starting is leading me to believe that I am actually on the rich side for the pilot and I'm having to compensate with an overly lean main jet and high clip. Im gonna scrap my efforts and go to 40/90 when I get home today.

    All things said and done, this carb is a cheap knockoff of a keihin PC20 and I'm pretty sure it will never perform as well as the real thing.

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