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?

Click here to add your own comments

Jun 11, 2010
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
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.

Click here to add your own comments

Return to Q&A Archives - Run Slow or Bog Down/Run Rough.

When you're done here, you may also be interested in reading some of these popular pages:

If you like to talk scooters, check out our motor scooter forums!

Battery Tender Junior in package

A battery tender like the Battery Tender Jr. can make all the difference in whether your scooter will start right up each spring, after being stored for months.

Just about every scooter owner needs to have a battery tender, sometimes called a trickle charger. Unless you are lucky enough to live in a climate where you can ride all year long, chances are your scooter will be put on ice, figuratively-speaking, for at least a couple months every winter.

One of the key steps in winterizing a scooter is to protect your battery from draining during its "rest" period. This can – and will – happen if you leave your battery sitting untended in your cold scooter over the winter, even if it's in a garage or shed.

Read our review or go right to Amazon.com to buy this highly recommended Battery Tender Jr NOW...


ATTENTION! I have had to delete the Scooter Forum for this site, unfortunately. Despite my best efforts, I could not adequately prevent daily attacks by hackers and spammers. Even though most of their posts did not go public, they still cluttered up my website host's server space, jeopardizing my account. I appreciate everyone's contributions over the past few years and I apologize for having to do this.

Wondering why your scooter question never got posted?

Chances are, there is a good reason. Did you...

If you "checked yes" on any of the points above, then I've deleted your post. Sorry, but I have standards. Feel free to re-submit, following the instructions I have everywhere on the site.

Also... all submissions have to be reviewed by me, and I am currently backlogged. Comments go live without approval, but still take 30 to 60 minutes to show up, so don't repost them, please.

This Week's Highlights

Share Your Scooter Blog Here
Your Help Needed!

We have lots of unanswered questions... can you help? Also, check out our newest eScooter Club members We are growing every week!

Keep Up to Date

Follow us on our Facebook Fan Page Follow our updates on Twitter
Subscribe to my motor scooter blog Subscribe to our RSS feed in your feed reader

Help Us Grow

Support This Site

I support this site by using affiliate marketing and running Google ads. I earn a small commission when you purchase items here, which helps to keep the site afloat. Thank you for your support.

XML RSSSubscribe To This Site

follow us in feedly
Add to My Yahoo!
Add to My MSN
Subscribe with Bloglines