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Post by Fox on Mar 25, 2015 19:09:21 GMT -5
Today I looked at a 50cc 139QMB powered scooter that has no spark. I tried a new CDI, new coil no luck so I checked for voltage on the two loose wires coming off the stator while cranking the engine without a spark plug installed to maximise the output. One black with red stripe I got 84VAC, the blue white I got .2VAC
Bad stator or pickup?
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tvnacman
Scoot Enthusiast
Posts: 408
Location: NYC
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Post by tvnacman on Mar 25, 2015 20:08:32 GMT -5
I would recheck the grounds 84 and .2 should fire off.
John
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Post by Fox on Mar 25, 2015 20:15:39 GMT -5
Thanks for trying to help me. I suck at electrical stuff. I forgot to add that I snipped the black white wire to the CDI to see if that would get a spark going and it did not so I reconnected it.
So which grounds should I check? The main stator plug is a large 2 pin with a white and a yellow wire. I have another 8 coil stator but it has a small three pin connector with a green wire, yellow wire and white wire. Can I swap out the stators and just ignore the extra green or should that go to... ?
I'm thinking maybe the kill switch went bad. How do you by-pass that for testing?
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tvnacman
Scoot Enthusiast
Posts: 408
Location: NYC
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Post by tvnacman on Mar 25, 2015 20:26:04 GMT -5
once you cut the black/white wire the kill switch is bypassed. Battery negative to the frame then to the engine. Then also the green to the coil, you could try to switch the wires on the coil.Check the gap between the p/u and flywheel.
John
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Post by Fox on Mar 25, 2015 20:50:05 GMT -5
Okay will do. I won't be over there til Friday but will post results of what I find. Thank you!
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Post by niz76 on Mar 25, 2015 21:06:41 GMT -5
Fox, I worked on a girls scoot (Peace Sports 139QMB 4t) with no spark and it ended up being the plug cap. I screwed the spark plug directly into the plug wire and got spark, but with the plug cap- no spark... just another idea for ya!
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Post by Fox on Mar 25, 2015 21:21:30 GMT -5
Yeah thanks Niz. I tried a whole different coil/cap that I have for testing purposes and still nothing. Electrical...
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Post by stevec on Mar 26, 2015 8:17:01 GMT -5
if it is grounded properly you may have a bad pickup not sending the signal to the CDI.
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Post by Fox on Mar 27, 2015 17:58:42 GMT -5
Okay so I got over there and pulled the flywheel and it turns out the pickup coil was hitting on the flywheel which kinda wore down the pole on the pickup some. I swapped in a used pickup and made sure it had some gap on the flywheel and hooray the spark returned. Then I start it and it won't idle. So after playing with the carb screws with no luck I clean the carb and reinstall it. Then I go to manually fill the carb buy drawing on the vac line and I found that the vacuum line to the petcock was completely rotten and disintegrating (massive vacuum leak = no idle) So I replace that and then I go to fire it up and it idles nice and I get it all adjusted yada yada. Then I start zip tying wires and hoses getting ready to button the scooter back up and I fire up the engine one last time before I start to put the plastic back on and the damn thing is coughing and sputtering. 5-10 minutes of cussing and checking later and I figure out that the plug cap decided it no longer wanted to grab onto the spark plug anymore and had popped off. Glad I had an extra one. Typical Chinese scooter repair day. Fix one thing and other stuff falls apart just cause you touch/move it
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Post by niz76 on Mar 27, 2015 18:13:29 GMT -5
Haha ya Fox it certainly takes some good troubleshooting skills and patience to overcome these Chicadee Chinas. Sounds like you fixed tha China outta that scoot! Well played sir.
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Post by Fox on Mar 27, 2015 18:26:33 GMT -5
Thank you! Yeah I get a little anxiety when I try to diagnose an electrical issue on these things cause it's my weakest area of expertise and I have actually failed a couple times and had to return scooters without fixing the issue which was embarrassing but not so today.
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