ATC90 Ignition Problem - Coil or Stator???

[c4dude]

New to the board - I've learned a ton just reading stuff here - nice job guys. I was afraid I was all alone owning a 3 wheeler - boy was I wrong!

I have a '78 ATC90. Had it for several years now, rebuilt the top end, cylinder, rings, valve job, etc. Ran great for awhile then I lost interest (boating!). Decided to get it back to running shape. Had carb trouble - decided to go with a new replacement carb. So far so good. Fires up fine, idles fine but after about 15 - 20 minutes, right after it heats up, it stalls. Plug is wet and dark in color. So I dropped the e-clip one notch (now in 2nd down from top, instead of middle) thinking it's running too rich. Now it run only on the choke, no matter where I set the mixture screw and throttle stop. So that reinforces ignition trouble in my mind. I've checked the points with an ohmeter, adjusted both advance and gap, still the same symptom.

It's tough to get it to fire so I've been suspecting a coil or stator problem. I pulled the coil (no small task as it's mounted inside the frame) and checked it with an ohmeter. It appears to be OK to me, but I'm not sure. Maybe a heat problem? I checked the condensor using by reversing the polarity of the ohmeter leads and it charged then went to infinity, both directions so from what I recall of capacitors, that's OK as a basic test to make sure it hasn't shorted or opened.

I checked the output voltage at the yellow and black wire coming off the stator. I got 24VAC between the black lead and ground, 2.6VAC between Yellow and ground, and 24VAC between the Yellow and Black wires.

I haven't seen anything that tells me what type of voltage I should see at the stator leads so I'm hoping someone either knows or has a running 90 and would be so kind as to take a voltage reading for me.

By way of comparison, I just picked up a little Honda Trail 70 project - CT70 I guess it's called. I pulled the plug on that as a comparison to see how much spark I see and that thing gets a lot more pops and a much brighter looking spark than the 90 is throwing.

I'm guessing I need a coil & condensor, but that's a pretty pricey part, especially if I guess wrong.

Can someone help a newbie out?

Thanks!

[0GravityMX]

try a new NGK! plug just for kicks and giggles ...ive seen new plugs that wont spart for s#!t.

[c4dude]

try a new NGK! plug just for kicks and giggles ...ive seen new plugs that wont spart for s#!t.

Tried that as well - even went to a Champion that's a little hotter heat range....same problem! Replaced the plug cap too.

[0GravityMX]

Have you tried cleaning the points?

[c4dude]

Yes, with emory cloth and then adjusted gap and aligned timing.

[0GravityMX]

hmm could be the coil getting heat soaked. let me check if i have one

[c4dude]

That's what I'm thinking...do you know if my stator voltages sound correct?

[0GravityMX]

honestly i couldnt tell you...i havent personally played around with any bikes that have points. hopefully somebody else can chime in on that

[c4dude]

OK. I'll see if anyone else chimes in. If I don't hear differently I'll go ahead and get a coil for it. Thanks for your help - I appreciate it.

[Texas 200x]

I had a problem with my 70 very similar to that it would run great with full choke, but bogged and missed with the choke off. I put all kinds of stuff on it. I push started it with the recoil of and I finally noticed that when I hit the gas the spark was jumping from the new points to the flywheel. I filed the actual frame of the points so they had more clearance and it fixed the problem. It may help you to pull the recoil off and see what is happening in that area. Good luck

[c4dude]

Thanks Texas. I've have left the points cover off so I can adjust the advance a little to "tune it in" while running and haven't spotted any arcing. I will pull the points and look for any possible contact with the advance plate. The 90 has the points mounted on the side of the engine, behind a separate cover, away from the recoil and stator. I can see where any path to ground from the breaker points would create a weak or intermittent spark. I'll give that a try. If that's not it, looks like I'll be purchasing a new coil/condensor and a new set of points. I'll update the posting when I know more. Thanks again.

[atc350xer]

New points coils aren't cheap! http://www.dratv.com/casig2.html

[c4dude]

I know! That's why I'm trying to make sure that's what I really need. I did spot another site that had the same coil for $80 - better, but still a lot of money!

[atc350xer]

I did spot another site that had the same coil for $80

Wanna share the link?

[c4dude]

Sure:

http://www.hyperparts.com/wc.dll?ctw...~1~0013~000229

I just ordered one. $95 including shipping and insurance. Still costly, but a little better than the $145 price I've been seeing elsewhere...