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Post by zoom on Mar 6, 2015 3:07:20 GMT -5
The scooter was running along fine and suddenly, it stutters in between revs for 10 seconds and cuts out.
Whenever i turn up the throttle it runs too low on gas and goes silent.
It doesn't want to start with the ignition button, only the crank.
on low revs it idles very nicely, it's just when i turn the throttle.
I have changed the sparkplug and cleaned the carb and put in another carb, same problem.
it sounds a bit lean too and the first candle had white residue on it.
What can it be?
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Post by JerryScript on Mar 6, 2015 4:54:50 GMT -5
Have you checked the valve lash? Also, check your spark plug boot, they have a tendency to become loose, and various vibrations from different RPMs can make it cut out. Had that happen to me last year, also could only kickstart it, played with the carb for almost two weeks thinking it was air/fuel when it was a bad plug boot (the spring-clip inside had broken off).
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Post by rockynv on Mar 7, 2015 9:47:31 GMT -5
Valve lash being out will eliminate intake pulse above idle so that it will no longer be enough to run the vacuum operated fuel pump or draw strong open the petcock depending on the bike. Also a failing ignition pickup can display similar symptoms to a lean condition and fuel starvation.
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Post by zoom on Mar 8, 2015 10:08:49 GMT -5
Thanks for the advice!  What is the valve lash? i have a reed valve on it it's a 2 stroke. what is the ignition pickup? I'm going to disassemble the entire cylinder and valve and exhaust, it's a catalyzed exhaust with 10k miles on it and 3/8th inch output on it, i don't think it's great. I just bought it at 10k miles so it's a good idea to check out in the output from the cylinder to the exhaust is crusty. The spark plug came out fairly white so it seems it's burning quite hot. When it's running at higher revs and i bump the front wheel up and down to rattle the bike it tends to miss some cycles too, i don't know why. |
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Post by JerryScript on Mar 8, 2015 11:30:13 GMT -5
Sorry, didn't realize it was a 2 stroke. I'll let those with more experience chime in, for now I would check the spark plug boot since you seem to be able to make it miss due to vibrations.
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Post by zoom on Mar 11, 2015 7:42:57 GMT -5
Perhaps the problem is related to spark timing?
It only starts on kickstarter,
It half runs with interrupting sparks at half speeds
i've checked the spark,carb,cylidnder,exhaust and have changed them all...
so am checking CDI problems now.
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New Rider
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Post by zoom on Mar 11, 2015 11:53:43 GMT -5
I checked the ignition capacitor, it was OK. The battery is low now, and there is no spark at all. I didn't change round the CDI box yet. I should do that next. other than that it's got to be the wiring or the roundey thing with the spools of copper around it. I'm figuring it's the CDI or the wires, will have it running again soon. Advantage is that i have a complete identical scooter to get parts from  and it was working until the crank drive went out of line. |
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Post by rockynv on Mar 12, 2015 5:03:40 GMT -5
Ignition pickup is a coil mounted near the flywheel that send a signal to the CDI to let it know when to fire off the spark plug. When these get weak or knocked out of alignment the pulse from them won't be strong enough to reliably trigger the CDI. On a 2 stroke you could simply be at the point where you have to decarbonize the exhaust ports.
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New Rider
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Post by zoom on Mar 21, 2015 6:51:52 GMT -5
Resolved: It was a connector that had come off of the ignition key block and it was shorting when i went over bumps... .it worked fine until i went fast and then it cut out intermittently until it stopped.
don't know why a cable can pull out of the ignition block but that's what happened, i don't know why i didnt notice by moving the key around... i noticed because moving the front panel in a certain way would stop the bike from starting.
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Post by JerryScript on Mar 22, 2015 2:55:17 GMT -5
Right on, glad you figured it out! Now enjoy the ride!
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