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General => Technical | How To => Topic started by: dbardell on October 10, 2018, 03:35:35 PM

Title: Kymco UXV 500 - No Spark Carb model
Post by: dbardell on October 10, 2018, 03:35:35 PM

This thing is driving me nuts.  Starts and runs fine for awhile, then shuts off.  Will not restart.  Let it sit overnight, and it will restart.

Last time, it sat idling for about 3-4 minutes and shut off, Checked and no spark.  Tried spark plug and no help.  Any sensors that will prevent this from starting that I can check ? 

Title: Re: Kymco UXV 500 - No Spark Carb model
Post by: CROSSBOLT on October 10, 2018, 04:59:48 PM

What tests have you done?

Title: Re: Kymco UXV 500 - No Spark Carb model
Post by: dbardell on October 11, 2018, 12:16:36 PM

Just the normal stuff.  Engine turns over fine.  Changed spark plug, checked wiring to coil.  Seems to quit when it is warm.  I was thinking maybe a high water temp shut off sensor, but not sure it it has anything like that.  But does lose spark when it quits. 

Title: Re: Kymco UXV 500 - No Spark Carb model
Post by: CROSSBOLT on October 11, 2018, 01:53:13 PM

Humor me: how do you know it loses spark when it quits?

Title: Re: Kymco UXV 500 - No Spark Carb model
Post by: Louder North on October 11, 2018, 04:33:22 PM

If it quits when it is warm, it could be a problem with the stator - small cracks become big ones when it warms up.  You can check it by measuring the output when cold and see if it changes when you point a hair dryer at it. 

Title: Re: Kymco UXV 500 - No Spark Carb model
Post by: dbardell on October 11, 2018, 11:29:55 PM

Quote from: CROSSBOLT on October 11, 2018, 01:53:13 PM

Humor me: how do you know it loses spark when it quits?

Pull spark plug wire and connect a good - new plug.  Ground on engine and try to start.  Original plug is left in head. No spark.  Yes, I have the engine cover removed. 

Title: Re: Kymco UXV 500 - No Spark Carb model
Post by: CROSSBOLT on October 13, 2018, 12:03:33 AM

Good answer. Louder North may be on to something since the "pulsar" is part of the stator. Any way to set up measuring for the service manual resistance of the pulsar coil when the spark fails?

Title: Re: Kymco UXV 500 - No Spark Carb model
Post by: hypophthalmus on October 15, 2018, 04:50:00 AM

Failing ignition coils can also be heat sensitive.

Title: Re: Kymco UXV 500 - No Spark Carb model
Post by: scooterfan on December 11, 2018, 06:45:43 AM

I experienced an exact similar problem on my 125 Agility. Eventually discovered that the CDI was causing the problem.
I initially saw a comment by someone who mentioned that a CDI just dies, and the engine will not start again. To my experience a faulty CDI does not behave like that.
When the CDI is on it’s way out, the engine start switching off suddenly during a ride, and will start again after a while. The engine switches off more regular as time goes by, but always starts after a while. Untill the CDI finally dies.


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