No Spark
 

I just wanted to pass on a recent find by someone I was assisting with no spark. We went thru all the Ohm checks of the stator and trigger coils, ignition coil. We measured ac voltage on each coil output and still no spark. Bike owner was about ready to order a new CDI and decided to just clean up his wiring harness. He untaped it around the coil area etc and got to the main harness. He found the black wire that is bolted to ground had broken off and was not attached to the harness. Most of these bike have a single point ground. One he fixed the problems, he went further into the harness and cleaned up other potential ground problems, he now has spark. Lesson learned.

So, if you have a no spark condition and everything else checks, verify that the ground is good. What I'd do is find a place or two on the solid black wire and add more grounds to the frame. make sure you scrape the paint off or rust off the bolt and ground away.

Steve

It is truly surprising how many folks start their fault finding other than at the beginning:
Fault Finding Guide - Motorcycle Electrical Fault Finding Chart - ElectroSport
The second sentence in that web link = "When you find that there is a problem, keep in mind that the number 1 problem with any charging system are bad connections".
Perhaps it should be the first sentence and highlighted in big type face/colour.:innocent:

Hi walkabout, I was the one Steve was assisting (thanks Steve!) just wanted to point out that your fault finding chart "assumes that the user has knowledge of the basics of electricity.. ..and about electrical systems on motorcycles in general" which I didn't, to the point of not even understanding what checking ground meant or how to verify wires!
If you know what you're doing then it might seem totally obvious but when you don't you might as well be trying to understand Chinese.
Anyway, the wire in question I tested from the ground point to where it connected to the main black wire on the harness but what I should have done is follow that all the way to the other end (there was a break hidden under the sheath on the harness). That's obvious to me now but at the time it definitely wasn't.

Might be better stated

"Over 80% of automotive electrical faults are bad connections"

So 4 times out of 5 .. it is a connection issue.

Which is why we started with the stator, checking for continuity and output. I will emphasize verifying the ground connection as well. Without that NOTHING will work correctly.

Naturally, a good clean ground point is just as important. Having had complete harnesses fully apart it is obvious that the method Yamaha and others use is just tapping into the wire and soldering the branch wire. This can lead to broken and corroded connections many times. On these old bikes, anything can and does happen. It just takes patience to sort it all out.

Very true... They're also one of the hardest faults to find unless it's an obvious component.