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Aftermarket Engine/Parts
Lifan
Re-jetting my Lifan Carburetor
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<blockquote data-quote="69ST" data-source="post: 172780" data-attributes="member: 5"><p>If you have the jet needle C-clip in the lowest groove, then it might be worth experimenting with the next larger size main jet. It'll have to be paired with a different jet needle height setting. The impact on WOT mixture will probably be around ~3% (educated guesstimate), the biggest change(s) will be at part-throttle where, somewhat ironically, it may actually run leaner. Generally speaking, jet needle height is used to tweak throttle response. With many carbs, WOT mixture is also affected. Not knowing anything about your, specific, metered air & fuel leak, I've no idea if yours works this way. Odds are high that you're in a good place with the WOT air:fuel ratio. That said, this is the peak of summer and you've no real way of knowing what, exactly, is in the tank. A subsequent fill-up may result in a leaner, or richer, mixture. Then, there's the cooler temps of late August to the end of the season, depending where you live & ride. Cooler air is denser air and that means leaner A:F ratios. That's the reason why I would want to do a little testing with the larger main jet...to have a safety/adjustment margin, on standby, ready-to-go if needed.</p><p></p><p>As for your low-rpm stumble, set the pilot airbleed (idle) adjustment screw 1/2 richer (clockwise) from its present setting. As long as it's at least 1/2 out (counterclockwise) from seated (closed) you should be okay. That will richen the mixture from idle to ~1/8 throttle. Hopefully, that'll at least minimize the hiccups...if not cure them. OTOH, if you're expecting EFI-like response, where the the throttle can be snapped open...fuggeddaboudit...aint gonna happen with a suction carburetor.</p></blockquote><p></p>
[QUOTE="69ST, post: 172780, member: 5"] If you have the jet needle C-clip in the lowest groove, then it might be worth experimenting with the next larger size main jet. It'll have to be paired with a different jet needle height setting. The impact on WOT mixture will probably be around ~3% (educated guesstimate), the biggest change(s) will be at part-throttle where, somewhat ironically, it may actually run leaner. Generally speaking, jet needle height is used to tweak throttle response. With many carbs, WOT mixture is also affected. Not knowing anything about your, specific, metered air & fuel leak, I've no idea if yours works this way. Odds are high that you're in a good place with the WOT air:fuel ratio. That said, this is the peak of summer and you've no real way of knowing what, exactly, is in the tank. A subsequent fill-up may result in a leaner, or richer, mixture. Then, there's the cooler temps of late August to the end of the season, depending where you live & ride. Cooler air is denser air and that means leaner A:F ratios. That's the reason why I would want to do a little testing with the larger main jet...to have a safety/adjustment margin, on standby, ready-to-go if needed. As for your low-rpm stumble, set the pilot airbleed (idle) adjustment screw 1/2 richer (clockwise) from its present setting. As long as it's at least 1/2 out (counterclockwise) from seated (closed) you should be okay. That will richen the mixture from idle to ~1/8 throttle. Hopefully, that'll at least minimize the hiccups...if not cure them. OTOH, if you're expecting EFI-like response, where the the throttle can be snapped open...fuggeddaboudit...aint gonna happen with a suction carburetor. [/QUOTE]
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Re-jetting my Lifan Carburetor
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