Running on two cylinders

[Gitbox]

#2 and #3 plugs aren't firing. I'm not getting +12v on the wires that go to the coil for those two. #1 and #4 have +12v. I think I may have a fried ignitor. The resistances from pin to pin don't match the service manual either. Any thoughts?

[GeeBeav]

You checked coil primary and secondary winding resistance?

[Gitbox]

Yes. Using stick coils. Swapping makes no difference.

[midnightrider]

Ohm the wires from the ignitor to the coils to make sure no open wires, check for 12v at the pin on the ignitor, should narrow it down. Sure sounds like a bad one.

[Gitbox]

Yeah, it was the igniter. I took it apart and found a bad 1uf 50v cap close to one of the switching transistors. Fortunately, I had one in my junk box. I also cleaned up a lot of questionable solder joints.


It seems to be running fine now. This happened once before on a ride and I thought it was some kind of fuel contamination because it cleared up after a few minutes. This time I had to limp home on 2 cylinders for about 15 miles. It actually got up to 55 mph, though. And talk about vibes...


Hopefully, it will last.


BTW, You can sure tell it's 80's circuit technology when you pop that igniter apart.

[bbroj]

Any chance you performed the resistance test on the replacement box? I had a thread going awhile back questioning if the readings listed in the shop manual were actually accurate. My readings for pins 4 and 5, on a working ignitor box, were almost completely at the opposite end of the scale from what was listed. I was polarity correct, and used several different meters. Interestingly, pins 4 and 5 are the outputs to the coils.

[midnightrider]

Yeah, it was the igniter. I took it apart and found a bad 1uf 50v cap close to one of the switching transistors. Fortunately, I had one in my junk box. I also cleaned up a lot of questionable solder joints.


It seems to be running fine now. This happened once before on a ride and I thought it was some kind of fuel contamination because it cleared up after a few minutes. This time I had to limp home on 2 cylinders for about 15 miles. It actually got up to 55 mph, though. And talk about vibes...


Hopefully, it will last.


BTW, You can sure tell it's 80's circuit technology when you pop that igniter apart.

Good for you. When mine quit, I took it apart and could see no obvious damage so I went to ebay and got another. After a very long google search, I found a place in Australia that does rebuilds on them, but the price was still higher than a used one off ebay. Maybe some day when good ignitors get hard to find, I'll try them.

[Gitbox]

bbroj, I did attempt the resistance test as outlined in the service manual and my readings on some pins were way off also. I used a Fluke 77 DVM. I gave that up and went old school on it. Electrolytic caps are common failures in a lot of circuits - take a look at badcaps.net.

[bbroj]

Thanks for letting me know. I had run the thread for awhile, with varying results, mostly the same as mine. I was trying to prove the book was wrong, in order to contact the publisher in hopes of getting future issues corrected, and letting folks here know of the problem. I am confident in the consistancy of my results on multiple, good running bikes ignitor boxes with various meters. The problem came when at least one or two trusted posters, claimed their results matched the book. For pins 4 and 5, if I reversed the polarity, I was much closer to the posted results. I may persue this with the publisher just to get their input.