Hello everyone I'm new to dirt bikes and this is my first bike . My issue is once I get the bike warmed up and I snap the throttle real quick it cuts out but if I barley touch the throttle it idles up real high for about ten seconds and comes back to normal idle . I've had the carb apart and haven't had any luck at finding anything wrong or worn or out if adjustment. I've tried going through the steps of adjusting the mixture but can't get anywhere with that either . Any info or help is greatly appreciated thank you for your time and consideration
bill32b
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6,049 Posts
Hello and welcome. Sorry for your first dirt bike headache. It does sound like a fuel problem, but other issues can exhibit identical symptoms. Ignition failures can fool you sometimes. You don’t mention how it runs when motor is cold and has choke on. Does it run okay with choke on? You may want to test it again with choke plunger on and see if symptoms persist. You may find motor runs better with choke on it may require a richer( bigger) pilot jet or possibly raise mixture needle and readjust idle mixture
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Good study. This should indicate your throttle response is a lean condition. You may want to try the easy way first. Lower the c clip on mixture needle from its current groove. This raises needle and richens your mid range fuel mixture. You may require richer pilot jet but try one change at a time and analyze results. It may require several adjustments to solve problem. Patience and perseverance will get this resolved.
Good study. This should indicate your throttle response is a lean condition. You may want to try the easy way first. Lower the c clip on mixture needle from its current groove. This raises needle and richens your mid range fuel mixture. You may require richer pilot jet but try one change at a time and analyze results. It may require several adjustments to solve problem. Patience and perseverance will get this resolved.
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only a guess
i can only guess. but jetting conditions dont change. engine conditions change (air leak, altitude change, fuel quality..etc) if you are sure the bike ran well with current jetting and it no longer runs well something has changed. valve clearance check and compression/leakdown test may help here. a worn engine or tight valve can affect carburetion as fuel signal changes. you sound like you have a good understanding of how the fuel system works. you didnt mention plug color, but i would guess it is lean. did it run well with current jetting and get sick? your post indicated this was recent purchase.
i can only guess. but jetting conditions dont change. engine conditions change (air leak, altitude change, fuel quality..etc) if you are sure the bike ran well with current jetting and it no longer runs well something has changed. valve clearance check and compression/leakdown test may help here. a worn engine or tight valve can affect carburetion as fuel signal changes. you sound like you have a good understanding of how the fuel system works. you didnt mention plug color, but i would guess it is lean. did it run well with current jetting and get sick? your post indicated this was recent purchase.
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pump it up
im not sure if those used a pumper carb. check your carburetor parts breakdown for presence or absence of pumper carb. post drawing on forum if needed. if you had carb open for cleaning, did you notice a small chamber on side? maybe post a picture if possible
im not sure if those used a pumper carb. check your carburetor parts breakdown for presence or absence of pumper carb. post drawing on forum if needed. if you had carb open for cleaning, did you notice a small chamber on side? maybe post a picture if possible
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Well good on you sir. You are a good study. Your grey plug is better than a white plug but a tan to brown plug is perfection. You can find aftermarket mixture screws from bike shops with an enlarged screw head for easier tool free adjustments that include your o ring. You will find those much easier to adjust with your fingers than fiddling with a screwdriver. Your motor could still be a victim of stale fuel. Because you only recently received bike perhaps it would be a good idea to drain fuel tank and clean strainer and start with a fresh batch of premium fuel(non ethanol if possible) if you still have carb off recheck pilot(small) jet and all passages in carburetor for debris or blockage. Best to use jet cleaner or welding torch tip cleaner or fine wire to ensure passages and jets are clear. It seems unreasonable to attempt resetting until you have thoroughly checked for other problems including rechecking carburetor. Check back as needed,good luck
Well good on you sir. You are a good study. Your grey plug is better than a white plug but a tan to brown plug is perfection. You can find aftermarket mixture screws from bike shops with an enlarged screw head for easier tool free adjustments that include your o ring. You will find those much easier to adjust with your fingers than fiddling with a screwdriver. Your motor could still be a victim of stale fuel. Because you only recently received bike perhaps it would be a good idea to drain fuel tank and clean strainer and start with a fresh batch of premium fuel(non ethanol if possible) if you still have carb off recheck pilot(small) jet and all passages in carburetor for debris or blockage. Best to use jet cleaner or welding torch tip cleaner or fine wire to ensure passages and jets are clear. It seems unreasonable to attempt resetting until you have thoroughly checked for other problems including rechecking carburetor. Check back as needed,good luck
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