Alpha Sports 50cc ATV No Spark
 

Hi everyone-

First post here, been lurking a while! I have a 50cc Alpha Sports Mini Cobra/Kolt I bought for my kids. They've ridden it for a few years and when I went to fire it up this year for a tune up, no spark! It's probably a 2000ish model, I don't really know.

So far I've unplugged the black wire to the CDI with no improvement. The tether safety switch in the rear is overridden, and the original key was lost so the previous owner simply wired in an on/off switch in it's place. I've gotten a spark once or twice, but oddly enough it's been when the handle bar kill switch was off, just from me messing around with it.

I took meter readings at the coil and CDI and here are the results. My meter does some weird auto ranging, so I just typed what it said rather than trying to convert and making an error.

Stator:
White/Red to black : .487 K Ohm
Black/Red to black: .850 K Ohm
Yellow/Red to black: .5 Ohm
White to black: .6 Ohm
Ground: 0 Ohm

Coil:
Primary: .8 Ohm
Sec at Cap: 3.5 M Ohm

The CDI on this quad has 7 wires, they are 3 bullets with black/white, black/red, white/red. It also has two plugs one with orange and black, and one with black/blue and brown.

I'm pretty stumped here, nothing I've done improves the no spark condition. I believe this quad is the same as the Polaris Scrambler 50, and going off the wiring diagram for that, I believe the stator and coil are bad. According to that the values should be:

Stator:
White/Red to black : 110 Ohm
Black/Red to black: 780 Ohm
Yellow/Red to black: .5 Ohm
White to black: .6 Ohm
Ground: 0 Ohm

Can anyone help? Wondering if I need to replace both those items. I haven't tested the CDI, not really sure how to.

Thanks so much in advance!

Could be an earth to run CDI. Some bikes are, so you need to try earthing the kill wire to see if that makes it spark. I've never found ohming out stators to do much good. Open circuit when you should get a resistance, something is wrong, closed circuit when it should be open, again something is wrong, but widely different resistances to what the book says, doesn't mean much.

OK, I assume you have fitted a new plug? Try checking if the stator's exciter coil is producing AC voltage when the engine is spun on the starter. Try checking if the trigger coil is producing an AC pulse. If they are, check if the ignition coil is getting a pulse from the CDI, this should be quite a high voltage. If it is, change the coil.

The trigger coil just pulses a voltage as the lump of metal sticking out of the flywheel flies past, not all that easy to test, as your meter may be "averaging" but it should be more than millivolts, though they vary so widely in output, it is difficult to say what is good. I would guess either trigger coil or CDI is at fault.

The wiring colours are different, but if you can work out which is which, it looks like being the one for those circa 2000, scooter based two strokes. A pity, as all you need is the trigger coil with the blue wire, the exciter on your machine is working fine. I note the trigger is adjustable for air gap, are you sure your existing trigger has the right gap between flywheel pip and trigger coil?

0.025" seems a bit wide, though I can't say I have ever adjusted one on the Chinese 2 stroke. I know Honda 200 engines were very critical on that gap, I had a Big Red that would only run on the absolute minimum. I would double check your info if you can. Annoyingly I have a workshop manual for a quad with one of those engines, fairly comprehensive, but the one thing it doesn't give is that air gap.

I repeat "I've never found ohming out stators to do much good." So I'm not surprised if the readings differ. It is whether they produce volts when spun on the starter. As your trigger coil doesn't seem to, you need a new trigger coil. If all you can get is the unit, you need the unit.