Surging idle

Hey guys, new to the moped world here. Had a buddy give me his 2010 Jonway 50cc. I had an issue with the idle surging on it own and sometimes stalling out so I decided to Replaced the carb, spark plug, plug wire, fuel filter, and battery. Still surging. Went to the air filter box and found a pin hole leak, so I sealed that up but still surging. Any suggestions? Possible sensor or electrical issue? I have a video but no way of posting until I upload to youtube.

Thanks!

Re: Surging idle

That's a scooter, not a moped...no PEDals. Some ppl here are touchy about that.

You replaced a BUNCH of stuff. Are the symptoms still the same (as in actually the same, not a different but similar behavior)? Is there an intake pipe between the carb and the cylinder? Might be an air leak between carb/intake/cylinder. The carb controls and meters the air/fuel mixture that is making it to the combustion chamber. An air leak can act irregularly and cause a bunch of headaches with idling, seen it on snowmobiles, dirt bikes, lawn mowers..... could also be something loose. Bolts on the intake and exhaust tight? (Intake being more important than the exhaust). Gaskets good all around?

What does it act like at other throttle positions? My guess would be that you notice it less at WOT.

Re: Surging idle

There's a bunch of dudes talking about this type of problem over at thescooterprofessor. These things have autochokes, a bunch of vent lines, emissions standards, you may have more luck there.

Re: Surging idle

I really appreciate the help. Had some time today to tear into the "scooter". Sprayed each line or joint going to the carb or cylinder with starting fluid while running and no change in engine rpm. Started to pinch the vacuum lines and found out if I pinched the one going to the petcock the motor smoothed out and ran cleaner. Swapped the line with a clear one and noticed the vacuum pulling fuel straight from the petcock to the cylinder... I'm going to replace the petcock and hopefully fix my issues. Big thanks for the help!! I'll follow up if this fixes the issue.

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