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Ported head on crf which way do I need to go with jetting

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Ported head on crf supermoto and put a cam on it. It's studdering and backfiring a little bit in mid range. Which way do I got with the jetting?  Thanks 

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Thanks y'all. I tried clicking the needle but it doesn't seem like it wants to budge either way?? I have a 170 main jet oem motor with ported head stage 2 cams and full yoshi? It's sputtering in mid range and back firing a little bit so I thought it was running lean? Bike was fine til I ported head 

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Raise the needle to the filth or six slot, see if that helps. Realize needle positions are a fine adjustment and if moving the needle up (raising/richening) helps, you'll need to eventually get a richer needle. If it makes it worse, you need to lean it out on the needle. If it does not make a change, then you either need to vary the straight diameter or look elsewhere for solution (test more).

However.... Cams and porting often cause a bike to need leaner jetting (because it is producing a stronger vacuum signal. Now, if what you really meant to say was the bike studders at steady throttle. (exactly where on the total throttle turn does this occur?) and it back fires on decel, that is a another matter entirely.

 

My bet is you are actually too rich on the needle (the studdering) and your backfiring is from having an open pipe, no ACV and coasting.

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Thanks guys. I've tried raising the clips and rejetted main from 170-172 and still studders mid throttle. Do I go bigger or what now?

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Thanks again. I got a jd jetting kit followed there instructions went with red needle and 180 main jet and the sputtering stop.  Now just trying to find the sweet spot. Feels a little sluggish threw all clip positions. Went to 185 and same result. Might try the 175 tommorow. 

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