Hi there
I am in the process of restoring my 1974 GP433. I have the majority of it back together after paint, rebuild etc. I checked inside the flywheel (coils, points etc.) before I put the engine back together. Everything looked okay, I lightly sanded the points that was it. Once back together I hooked up my test light and pulled the engine over and had good power to both mag and pto cylinder coils wires.
I hooked up the rest of the wiring harness to the lead out of the engine (grey coil wire, orange coil wire, green wire, red/white, wire). There was a yellow and solid red that didnt have any wire to connect too in the harness. So here is the issue:
-With both mag and pto coil wires connected to the respective coils, only the mag coil creates spark. The pto does not spark but has some voltage from my test light.
-With the Mag coil wire disconnected the pto coil does create spark.
-With the pto coil wire disconnected the mag does not create spark. There is power to the pto coil wire from test light.
-with both coil wires disconnected, there is only power to the pto (grey) wire
I've tried both coils with different wires and both work so all good there. I've tried with and without the harness hooked up to the key ignition, no difference.
The wiring harness was hacked up but continuity appears in all wires. All connections are good. The only thing is it doesnt have a kill switch...but that should affect since I can get spark from at least one coil depending on the wiring.
So Any help is greatly appreciated. I am no expert on these old ignition systems but throw anything you have at me I will learn. Also i will upload the wiring diagram I have. You will see I have one wire labeled as ? My sled has a solid red and solid yellow which are not in this diagram.
So ground problem? Internal problem? Some mysterious wiring I cant see? Again any help greatly appreciated, I've been spending the last year restoring this and really want to see it run soon.
Thanks
Spencer
1974 yamaha gp433 ignition problems
