Zx50 runs for 10 miles then stops!!! CDI?

[Olof]

Hi newcomer here... Need some help. My zx50 2003 runs great for 10 miles then loses power for a split second. After a minute it shuts down almost completely; i can still run it on idle but touching the throttle, it stops completely. It starts ok again but can only idle. Try to rev it, it stops. Now, Leave it for a day, and I can drive another 10 miles. Same thing again. I've had the dealer clean the carb, replaced the ignition coil. New sparkplug, clean air filter new battery.  At loss, hard to fault check since it's so unpredictable. Can it be the CDI-box?  Can it work so so, or is it either or?
Thanks for any advice! Cheers

[cors50agility]

You need to do some investigations when it stops.
Take with you some tools(including gloves)
Ride it 10 miles.
When it stops check the carburetor fuel bowl for fuel and/or fuel level.
Pull the spark plug out and check for visible spark.

Return the info to the forum.

[Olof]

Hi thanks for advice! Fuel and spark OK when hot, no vacuum in the tank and fuel flows plenty when I unscrew the fuel bowl screw. Ordered a new CDI-box today. Haven't replaced the stator but reckon the stator, if susceptible to overheating, should be hot fairly quickly and not after 45 min of driving. Strange that it can run so fine for such a long time before it happens. I've taken all connectors apart and sprayed WD-40 on them as well. 

[LoveMyKymco]

Hows the compression? If you think its a cdi or coil over heating issue let it idle for that long, those two parts dont get hotter the harder they work really so if its an overheating resistor itll show itself.
Those were all good things to check tho for sure. keep on trying!

[Olof]

Still waiting for the CDI so will see... You may be right it's just so weird that it runs so well, strong uphill at 30 mph unmodified. Does so for 45 min then a sudden hickup and in a matter of second just wants to idle. You'd think with the piston overheating, it would gradually become weaker over a longer time than a couple of seconds. 

[Olof]

CDI arrived today, I dare say it was the issue. Touch Wood. Driven 20 miles today and the new CDI lets me crusie evenly at 28 mph. The old one kept cutting in on/off at max speed. Old one was an original Kymco whereas the new one was a cheaper third party replacement. So far so good...

[LoveMyKymco]

28 mph is extremely low for a zx50, cruising should be near 40 all the time with slowing down up hills at no less than 30.
Congrats on finding the issue tho!

[Olof]

This one is restricted (Sweden) so it's a matter of being legal. I know, i'm a bore...   Unrestricted it's regarded as a motorcycle. This way I can use the bike and pedestrian lane which makes all the difference in the city, dodging all traffic jams. I'd get pulled over in  no-time doing 40 without license plate unfortunately... The low gear ratio is fun though uphill redlights.
Anyway, what makes these CDIs brake down all the time? Same day I got home with the new CDI, my daughter's zx50 wouldn't start. No spark so I swapped her old CDI with my new. Started up right away. When I was at the dealer, he had a bunch of old zx50 he was fixing up to sell. He wanted me to try out a used CDI before ordering a new replacement. He opened up five zx50's. Every single one had their CDI nicked. He wasn't surprised though as it's the first part to be nicked from an old one, he said.
Has anyone got a theory? The spark plug calls for a resistor type, could it be that some don't care and put in a wrong type, thereby stressing the CDI? All other components are so well made.

[Olof]

BTW, one connector on the CDI has four wires. On the receiving connector to the main system, there are only three; the light green from the CDI has no matching counter part. Is this a restriction on mine? Where was the light green meant to go?