Huasheng 49cc Idling/Carb Issues

Discussion in '4 Stroke Bicycle Engines & Kits' started by Moka'sMotorCreations, Feb 3, 2019.

  1. Moka'sMotorCreations

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    Hello! I tried searching around here before making this post, but couldn't quite find the same symptoms that my engine was having...

    I have what I'd assume is an unbranded 49cc Huasheng 142f, and it suddenly started acting a bit weird... Before today, it would idle well, and had plenty of power. The overall gear ratio is set to top out at about 32MPH @ ~7500RPM, and it has done so consistently...

    But today, after taking it for a rather short spin, the engine seemed to want to idle very high. If I lifted the rear wheel up, the engine would spin it faster until it hit maybe 3500-4500 RPM... Even if I took the idle screw completely off, it would continue to idle very high. Turning the choke on or off made seemingly no difference.

    I tried riding it again, and it still seems to have the same top end power/speed, though I think it sounds a little different (or maybe it's all in my head)...

    My first thought was to adjust the mixture screw on the left side. I screwed it inwards quite a bit until the idle lowered, but now it's extremely erratic. It will idle well for a second, jump up high, or very low, and repeat in no specific order, until it finally dies

    I've tried taking the carb apart and cleaning out the low speed jet, but to no avail. I did notice that the gasket between the carb and the engine seemed a bit rough, but I'm not sure if that's truly the issue, because as far as I'm aware, that wouldn't explain a high idle.

    Another small but possibly important detail... Sometimes when the engine dies or fails to start, it'll make a small "puff" noise and the carb shoots mist/smoke backwards.

    I'm not really sure what the issue is, but I'm fairly certain it's something to do with the carburetor, or possibly the valves. Any help or redirects to similar threads would be appreciated! I was planning to replace the carb with an NT setup, but it would save me money to keep it running stock for now.
     
  2. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    I concur... it sounds like either a air leak or the valves went out of adjustment
     
  3. Moka'sMotorCreations

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    You might be right... After pulling the carb off a second time, the gasket seems damaged. It looks so cheap, thin, and dried out...

    Also, I did some research on general signs of intake leaks, and the symptoms match spot-on. Gonna get some gasket material so I can make a new one. Will give updates as I go.
     
  4. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    I advise just swapping it all out now for the NT carb & manifold. ;)
     
  5. Moka'sMotorCreations

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    Agreed! Was eyeing it today. Do you have any tuning experience with those on the Huasheng? If so, would you know what jet should I get for it? (I'm at 36' altitude) Or does the stock NT already work well?
     
  6. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    The stock NT jet is a little small, so I re-drill my jets with a tiny 'jewlers' drill bit set...
    I drill the jet about 2-3 sizes bigger for the 49cc 4-stroke engines.
     
  7. Moka'sMotorCreations

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    I'm surprised. I would have expected to downsize because I know they usually come with the 66cc 2 strokes. Would you happen to know what jet size number that would be? I'd prefer to just order it but if I have to drill it myself I guess I can give it a shot.
     
  8. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    I just checked... I drill the jet to #68 (.031")
     
  9. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    #68 = 78.74mm jet size.
    stock NT is a 70 jet.
     
  10. Moka'sMotorCreations

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    Hey, just giving a long-needed update! The problem indeed was an intake air leak. I got some red RTV silicone from Harbor Freight, applied it over the old gaskets, and let it cure. It runs even better than when I first got it, which leads me to believe this problem has existed from the start but got worse over time...

    I'm thinking the engine has been sitting in the warehouse in poor conditions for quite a while. Another problem I've had with it was the grease in the clutch bushing being all dried up so it would friction-lock and kill the engine. I was able to fix that by disassembling, cleaning, re-greasing, and rebuilding it.
     

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