Guys, I've just ordered a new engine from ebay which has two plugs. One of them I think I've identified as the alternator output and ignition trigger. I found three of the pin had a resistance of 125-0-125ohms, and another that had a resistance of 500 ohms.

There is a 2nd plug that I can't figure out what it does.... 6 pin plug with 5 wires. On the original engine, there is a 2nd plug that is the gear indicator. I've shifted this engine into Fwd and Rev and can't find continuity... all combinations I've tried read overrange on my meter. So I simply don't know what this plug does.

Here's my dilema... the tao tao jeep 125 has a different plug for the alternator and ignition. So I'm wondering if it's practical to change the alternator stator over on these two engines. it would save me the trouble of a cobbled (re)wiring, but on the other hand, how do you set the timing on these things?

So should I swap the stator or figure out the wiring on the new stator?

 

Ok, not a lot of answers here... but....

I did end up swapping the alternator and cover plate from old to new engine. I have spark, will have to get a timing light and look in the little access hole to see when it's firing. I don't know what to do if it's not right, there doesn't seem to be much (any) adjustment. The inside diameter of the two flywheels are .050" different. I rotated the engine by hand with a ratchet and heard no scraping, so proceeded.

As I said, I do have spark, and I do have 150psi on a compression test. The old engine leaked air into the case and didn't have the comforting crisp feel of the new one when I turned it by hand. So it's probably got a cracked piston.

I do have a spare carb from my tinkering, I've been resisting using it, but I'll probably install it tomorrow. The current carb is leaking fuel out the float bowl now and then, so it may be screwed too. Ether isn't working... I know I'm moving in the right direction though... at least the better compression test is nice.

 

so is it the factory spark plug or an NGK? once in a while you'll get a quad that'll test good for spark but dies when inserted in the jug/cylinder. i've had this happen to me before .

 

Thanks for the response. I have one of each plug, the stock and one I got from the local moped shop. Both give an intermittant spark. Honestly, with a hot battery, the plug seems to spark when held against a ground, but if I keep cranking it, it gets intermittant. I can't hear any difference in the RPM of the starter... and this model alternator/stator has dual coils (one for ignition power, one for battery charging) and the ignition trigger. So it would seem that battery voltage would not be an issue except if the engine it's turning fast enough to make the juice to run the CDI... but it sounds like it's spinning at the right speed.

Anyway, I think I'm going to have to break down and just rewire the whole JEEP for a single alternator output... at least this way I'll have 12v to run the CDI and I'll just hook up the ignition trigger for now... maybe it'll be easier to troubleshoot.

 

It got a little warmer this weekend, so I spend a little time figuring out my new ebay engine.

I learned:
red/bk is ignition power to CDI
bl/wh is trigger pulse for ignition
yellow and white are alternator outputs.
green ground.

The other plug is the gear shift indicator.

I've had to rewire to a 6 pin ignition module, but I may try to go back to the original 4 wire CDI now that I know what the wires are.

Right now the only thing I'm missing is the kill switch. I have to ground a wire back on the engine to stop it. Easily solved.