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Aftermarket Engine/Parts
Lifan
New 125 Sputters through all throttle/idle
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<blockquote data-quote="69ST" data-source="post: 180643" data-attributes="member: 5"><p>Never tuned a PD series carb. That fixed-height needle causes anxiety. I'd be thinking seriously about using a different carburetor...one that's more tuner-friendly, or at least less tuner-defiant, than this one. That said, all is not lost. If you can source the right size flat washers, you could try using them to adjust needle height. One washer should be close to one groove, in an adjustable needle. That should give you some indication as to whether, or not, this carburetor can be dialed-in well enough to use. Based on your results, so far, I'd guess 1-2 washers ought to do the trick...if they're going to. And, I'd guess that you need 3mm washers. Any decent hardware store should have them and probably in stainless steel, as well as zinc-plated steel...cheap, too. </p><p></p><p>The main possibilities...</p><p>You win the lottery on the first or second try. IOW, 1-2 washers do the trick.</p><p>It goes too lean, in which case, the next step would be a larger main jet...seems highly unlikely.</p><p>WOT mixture goes pig-rich, regardless of part-throttle results (even if those are excellent). With some carburetors, WOT mixture is affected by the jet needle. In the event that this carb is one of them, it's entirely possible that the non-adjustable jet needle will be too short to raise, using washers. If that's the case, that last little bit of throttle opening could result in wildly excessive fuel flow through the main jet.</p><p>Contact a vendor who supplies Keihin parts, there may be a choice of jet needles for this carb. If there is, I'd bet that you can find one that does the trick...either with adjusting grooves (and corresponding added length) or different tapers.</p></blockquote><p></p>
[QUOTE="69ST, post: 180643, member: 5"] Never tuned a PD series carb. That fixed-height needle causes anxiety. I'd be thinking seriously about using a different carburetor...one that's more tuner-friendly, or at least less tuner-defiant, than this one. That said, all is not lost. If you can source the right size flat washers, you could try using them to adjust needle height. One washer should be close to one groove, in an adjustable needle. That should give you some indication as to whether, or not, this carburetor can be dialed-in well enough to use. Based on your results, so far, I'd guess 1-2 washers ought to do the trick...if they're going to. And, I'd guess that you need 3mm washers. Any decent hardware store should have them and probably in stainless steel, as well as zinc-plated steel...cheap, too. The main possibilities... You win the lottery on the first or second try. IOW, 1-2 washers do the trick. It goes too lean, in which case, the next step would be a larger main jet...seems highly unlikely. WOT mixture goes pig-rich, regardless of part-throttle results (even if those are excellent). With some carburetors, WOT mixture is affected by the jet needle. In the event that this carb is one of them, it's entirely possible that the non-adjustable jet needle will be too short to raise, using washers. If that's the case, that last little bit of throttle opening could result in wildly excessive fuel flow through the main jet. Contact a vendor who supplies Keihin parts, there may be a choice of jet needles for this carb. If there is, I'd bet that you can find one that does the trick...either with adjusting grooves (and corresponding added length) or different tapers. [/QUOTE]
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Lifan
New 125 Sputters through all throttle/idle
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