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Thread: Whats an Ideal Carburetor for a Lifan 110CC Engine

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    Joec03's Avatar
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    Whats an Ideal Carburetor for a Lifan 110CC Engine

    I bought a way too big carb and I'm getting fed up trying to dial it in with jetting. Can anyone suggest an ideal carburetor for a Lifan 110CC auto-clutch? I'm running it on a CT70.

    I want to be able to just bolt it on and be good to go. I'm tired of my motor bogging out.
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    code3k5 is offline 120cc
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    This one


    ---------- Post added at 02:45 PM ---------- Previous post was at 02:42 PM ----------

    they are sold with a 19mm Walbro or Sheng Wey carb

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    My preference would be a genuine Mikuni VM20.

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    If I were to get this with 110cc jetting should I be good to go? Hooper Imports Experts on Chinese Motorcycles and Parts, Engines - Product Detail
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    MIKUNI VM (ROUND_SLIDE) CARBS

    This would be my preference. Price-wise, nowhere near enough difference to be worth worrying about, at least imho. Your opinion may be different. I would, however, suggest asking yourself if an extra $35 would have been money well spent if it had allowed you to cure your driveability ills?

    The key, imho, is product support, i.e. availability of parts (mainly jets, in this case), if needed. Mikunis & Keihins are top quality carbs, with reasonably broad parts & tuning support. They have been for many years.

    Any time you source a carburetor separately from an engine, you can expect to do a little bit of tweaking to get it completely dialed-in. The only exceptions are carbs that have been spec'd for a particular engine...and of course, luck.

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    I'm willing to buy the mikuni but how much tinkering will be needed on the jets? What size jets should I order from dr atv? I'm located approximately 640 ft above sea level.
    Last edited by Joec03; 06-04-2011 at 05:45 PM.
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    Educated guesses...

    20 or 22.5 pilot jet should be right. #180 main is probably going to be too big. If I were sourcing this carb for this engine, I'd include the smaller pilot jet, along with #150, 160 & 170 mains.

    The tuning process begins with getting idle dialed-in, which is dead easy. If the motor runs rich at idle with pilot airbleed screw 3 turns out from seated, you need a smaller pilot jet.

    With the main circuit, you start by finding the rich limit at WOT. That usually means the largest main jet that still allows the engine to rev-out cleanly at WOT. I say usually because jet needle height has some effect on WOT mixture, contrary to what some tuners believe. You may end up with a situation where the leanest jet needle setting (top groove) allows the motor to rev-out, while the richest needle setting (bottom groove) puts the engine into overrich territory with one size smaller main jet. If that happens, you'll use part-throttle driveability (i.e. best/smoothest throttle response) as the basis for your decision.

    If this strikes you as tricky, or mysterious, relax...it isn't. This will boil down to one jet size and/or one jet needle groove between rich misfire and revving-out cleanly at WOT. And, once you start riding more or less normally (non-test mode), you'll find that it comes down to 2 jet needle clip positions which provide acceptable results; one will be better than the other.

    Once you have the carb dialed-in, it will remain that way unless there's a major change in operating conditions. Come fall and 20-30 degree cooler ambient air temps, you might need to tinker with the idle settings and that's about it. I don't know if your side of the state is forced to deal with seasonal pump gas formulations. Over here, on the "sunrise side" we we are. Worst case, that has translated into having to move the jet needle height by one position. That's pretty much carb tuning 102, in a (very large) nutshell

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    What intake manifold would you recommend for that carb. I'm looking for a turned out intake so I can use the same air filter I had on the china mikuni. I'm having trouble finding a turned out one on dratv, if you could link me I'd appreciate it.
    Last edited by Joec03; 06-05-2011 at 05:20 PM.
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    I was able to find a turned out intake manifold which dratv recommends for Lifan engines. LEFT_TURNOUT 22MM MANIFOLD_KIT GREAT_FOR_SWAPS (TBQ22KIT) It has a 22mm opening and I measured my motors intake port and it is also 22mm. This intake seems ideal, but then wouldn't a 22mm carb also make more sense so everything is the same size?
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    You're mostly on the right track. I'll try to keep this post a semi-reasonable length, the tech explanations are lengthy.

    A 22mm intake manifold should be fine bolted to a 22mm intake port, as long as the alignment is perfect. That's easy enough to accomplish. If space permits, install the heat insulator between the manifold & carb. It'll improve fuel atomization and is slightly more important with a 22mm intake than with a 20mm intake, which would also be fine. In your shoes, I'd probably source the 22mm intake...it'll be usable should you ever decide to source a larger L125-140 in the future.

    As for carb size, "you can't push with a rope". An engine can only draw so much air. Beyond that, all you'll accomplish is slower airflow velocity through the venturi and the headaches of trying to tune around lazy fuel circuits and lean spots. 18mm is sufficient to feed your L110. A 20mm carb is 23% larger, 22mm 50%...airflow velocity decreases by the same percentage venturi diameter is increased.

    That's why, for anything other than an all-out race machine, you're best off running the smallest carb that doesn't restrict engine output. A carburetor has to be seriously undersized to be a restriction. A VM22 can support roughly double the hp produced by your motor.

    So, regardless of whether you opt for the 20 or 22mm intake, I'd still recommend the VM20 carb for your motor, over the VM22. That's more than big enough to have peace of mind that you're not leaving any hp on the table and still have a reasonably tunable metered fuel leak.

    The VM22 is tough enough to dial-in on 110 Honda Nice motor (which is rated @ 9.5hp, stock), as in "on the ragged edge of practical". On a 6.5 - 8.0hp L110 it mostly likely will not be completely tameable.

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