1996 Yam 115 Electrical Problem

[jmichel]

I have a 1996 115 Yamaha C115TXRU, and after running great for two days, and sitting for two days, it decided not to start. It would crank, but it was getting no spark. Changed the CDI, and it started right up, but two cylinders were dropping in and out due to weak spark. I can pull the plug wires, and hear them ticking, but the engine doesn't get any rougher on the idle when I pull the left side cylinders wires. If I pull the right side, it almost dies. Ohm checked everything according to the yam book, and the only thing not reading good is the rectifier. Could the rectifier cause that? Doesn't sound right to me. I figured the coil pulser, or the stator, but they look good. It makes no sense to me. Is there a running check that I can do? The Yamaha service manual only has an ohm check. I'm confused! Any help would be greatly appreciated. These parts are all expensive, and I really don't want to buy something that I don't need. Thanks, Jeff

[Hamfisted]

Did you unscrew the plug wires from the coils and check their ohm resistance ? I've found oxidation on the ends of the plug wires that's virtually killed the spark on a few cylinders. The plug wires just screw into the ends of the coils. Use some dielectric grease when you reattach the plugwires to the coils to help keep out moisture and corrosion. You can also get a truer reading of the coil Ohm test this way. Its possible you have a couple of weak coils too. Try swapping the coils around and see if the problem moves with them. Good luck.


Mike

[jmichel]

I did what you said, and it's still doing it. The coils, and the wires checked good. I even swapped them. The only thing that looks bad is the rectifier. Has anyone ever heard of this affecting cylinders firing? It's intermitten. Any help would be great. Thanks, Jeff

[ROB]

Jeff I have a 1997 115c that had the same issues.
First I found one of my two batteries bad.
It would start and all, but under a load test it failed. This helped, but ultimately the rectifier
was bad too.I swapped coils ect.. just like you.

[Ken]

Jeff,
I haven't had much experience in this area, but I have to agree with you that it doesn't make much sense that it would be the rectifier/regulator. You would think that would effect all cylinders.
Take a look at the electrical section in your Yamaha manual. There is a section in there on checking spark. Maybe that will give you a clue.
Good luck,
Ken K