Sudden change in carb performance

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Sudden change in carb performance

This is a discussion on Sudden change in carb performance within the Chinese/Import Minis - General Discussion forums, part of the General Talk category; I have an SSR 140tx that was running great for about 2 years of light usage just running around the farm. Starts EASY. It idles ...

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  1. #1
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    Sudden change in carb performance

    I have an SSR 140tx that was running great for about 2 years of light usage just running around the farm. Starts EASY. It idles perfect and steady in the middle of the pilot screw adjustment range and still does. Its had regular valve adjustments and oil changes, so everything is running and adjusted properly.

    Recently, I'm getting what seems to be a super lean off throttle bog, sometimes killing the engine. If I SLOWLY roll on the throttle, it runs ok, but even a slightly quicker throttle application would result in the same feeling as when the gas tank runs dry.

    If I slowly roll the throttle to 1/3 through about 5k rpm, then it runs normal and I can give it the beans however i feel.

    Since the bike has been used regularly and was running fine in all weather conditions, I don't think this is a fueling issue even though the symptom present itself as so.

    Things I am thinking:
    stretched timing chain?
    time for new piston?

    What else is a wear item that can cause this?

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    Sudden change in carb performance

    The first thing I would check would be the pilot jet as the opening is very small and prone to clogging.

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    I did check the pilot jet, and can see light through it. I sprayed carb clean through it and all the pilot circuit as well.

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    dirtbkr188's Avatar
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    If the carb has an air screw, try turning it IN a 1/4-turn and see if the hesitation lessens. If the carb has a fuel screw, turn it OUT to slightly richen the pilot jet circuit.
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    Although you can see light, it could still have restricted fuel flow.

    Last week I cleaned a friend's Honda ATV carb as it was not running well. I could see light through the pilot jet but I cleaned it throughly anyways. Bolted it back on after cleaning it and it runs perfect now.

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    How did you clean the pilot jet? Also, any way to make sure my pilot circuit itself is clean, besides blasting carb cleaner?

    Also, if the pilot het/circuit was clogged, wouldn't I have an idle issue?
    Last edited by damnbiker; 06-05-2017 at 03:15 PM.

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    Sudden change in carb performance

    clogged pilot jet on a CRF50 - Success!
    https://www.thumpertalk.com/index.ph...0---Success%21

    Different carb, same process.

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    A local bike shop near me has a hot ultrasonic dip tank with a 50/50 mix of Simple Green and water. A 30 minute dip with the carb completely disassembled is usually all it takes to clear out the inner passageways.
    - dirtbkr188 -



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    I wonder if my wife's ultrasonic jewelry cleaner could clean jets also?

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    Probably so, but you might not survive !!!!!

    Don

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    Dipped the carb into my friend's ultrasonic for 30 minutes....sadly no change. Safe to say its not any blocked passsages in the carb causing my problems. Also put in a new plug, no change.

    I am really stumped what could cause a perfectly running bike to just start acting up so badly???

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    Did you try adjusting the air or fuel screw accordingly?
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    Try just getting a new pilot jet. If the issue is still there you may have an air leak or not jeted properly. I usally rejet depending on weather on my mod bikes.only time keep same jets are when it's completely stock.

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    Quote Originally Posted by jamesfl View Post
    the first thing i would check would be the pilot jet as the opening is very small and prone to clogging.
    ^^^^ this !!
    T Bolt USA - Let's go riding!

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    The bike had a 35 pilot jet inside. I tried putting in a new 38 without changing the fuel screw, which resulted quite a rich idle. It will die on choke. The off throttle bog (like no gas) is still there, but a tiny bit better. Its more resistant to dying now. BTW, I blew out all the holes I could find with 125psi compressed air and verified that carb cleaner shot out the other end. The bike has been run regularly, so unless something solid went through the fuel filter, I highly doubt clogged passages.

    I adjusted the fuel screw to keep it running on choke, and there is no bog on full choke. This eliminates everything EXCEPT carb problems.

    It does seem like air leak symptoms now, like the transition from idle circuit to needle opening is getting ultra lean. If I give it enough throttle to get into the needle controlled zone, the bike runs great up to WOT. The needle and main are already set slightly rich, so I don't want to richen that circuit any more.

    I sprayed some carb cleaner around the fuel screw and intake gaskets, but no change in RPMs.
    Last edited by damnbiker; 06-12-2017 at 06:00 PM.

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