Why won't my Kymco KB 50 scooter run above idle?

by Scotty
(Selfkant, NRW, Germany)

I have a 2003 Kymco 50 scooter and it has been running fine up until yesterday. My wife and I were out riding and for some reason it just stopped running properly.


I changed the spark plug, coil, and fuel filter. I cleaned the carb inside and out and found no contamination. Can't believe I am stumped by a two stroke. Thanks for any insight.

Comments for Why won't my Kymco KB 50 scooter run above idle?

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Jun 11, 2010
 CDI
by: smoguy

I bought a new CDI but when I went to start the scooter up with the old CDI it ran just fine, so I took it on a ride around the block with the new one in my pocket. The scooter starting acting up about 5 minutes into the ride. I put the new CDI in and it has ran fine so far. I checked all the wiring and connections as well cleaned connections. Hope this is fixed. Thank all of you for your input.
Jun 07, 2010
 Maybe
by: Jim Zeiser

It could be a bad CDI but they usually come back to life after a short spell. I'd start looking for a bad connection somewhere that got jostled when you moved it around then shook loose from engine vibration. It's so common on scooters.
Jun 07, 2010
 New Development
by: Scotty

Thank you for the comments, I will try those things, but a new development. I went to start it this morning and it ran great, for a couple of minutes then the same thing again. Now it will not start at all. I wonder if the CDI is bad. I used to tinker with old small gasoline engines but the didn't have the CDIs there no way to ops check them short of replacing it.
Jun 07, 2010
 Vacuum Line
by: Jim Zeiser

You have a vacuum leak somewhere. I would look for a hose that fell off or a hose that tore. When you open the throttle, too much air is being introduced and the overly lean mixture is stalling out the motor. If you put your hand over the opening to the air filter it would probably keep running and you'd see what I mean.
Jun 07, 2010
 Kymco won't idle
by: Izzy

It sounds like the Reed Valve has gone bad. The reed valve opens up and allows more gas and air into the the combustion chamber. It sets behind the carb. intake, next to the cylinder head. I would take it out and try cleaning it first. If that doesn't work, replace it with a new one. I hope this is helpful.

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