Engine revs high once clutch is pulled in then slowly idles lower until it dies

Greg58

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Does it rev high when cold or does the engine have to be hot? Compare the temperature of this engine to a proper running engine, this engine is probably way hotter. If not an air leak it could be that the jet is too small, I've had a kit carb that was not a true NT that needed opening up. The bofeng carburetor that several of us have tried shows a lot of promise, maybe try a different carb and see if that helps.
 

Jaycee604

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Does it rev high when cold or does the engine have to be hot? Compare the temperature of this engine to a proper running engine, this engine is probably way hotter. If not an air leak it could be that the jet is too small, I've had a kit carb that was not a true NT that needed opening up. The bofeng carburetor that several of us have tried shows a lot of promise, maybe try a different carb and see if that helps.
Revs high after its warmed up. I personally hate the bo feng ones. Old nt style worked better for me. Im waiting on the jets to come in. I have tried the old and new nt carbs and a clone dellarto which was by far the s**ttiest one lol.
 

Chainlube

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You talking about the big screw on top of the carb that holds the needle and spring?
No. Under the carb is a cable support screwed into the case. Every once in awhile the carb will hit that and not seal right. Post a picture of your carb, someone might notice something that got overlooked.
 

Jaycee604

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You mean the cable that guides the clutch cable to the arm? All my bike have an offset with reed valve so its very far from that
 

Daytripper24699

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So i have made several of these bikes. But this problem is getting anoyying with this build. After i pull in the clutch while coasting or getting ready to stop (obvs while engine is on) it revs half throttle (sounds high) then Slowly relaxes until it eventully dies. I adjust the idle screw and know how to use it. This does nothing, the carb needle is tuned to rich like all my bikes, only upgrade on this on is high performance cdi and some port work on the jug. Could this be an air leak near intake? It also takes slightly longer to start then my other bikes. Let me know what you guys think
Air leak or loose throttle cable...
 

Karl Snarl

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You be talking to a guy who left in a huff, because he knew more than anyone else here, so your comment is falling on deaf ears.
They all know everything, and never return after they burn the motor up. Unless to say these engines are junk. I'm impressed at how good the engines have become, since I started this journey. China has really been stepping up their game. Not to say the reject pile doesn't still get sold, but most the brand names ( we all know who sucks and buys those rejected engines) are good engines.
 
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