1984 VF500 No spark on front two cylinders?

Hello there I am green to the online forums and thought I would give it a try. I have recently bought a 1984 Vf500 interceptor as a non-runner. I have it where it will run if the throttle opened and held at 1500 rpm and dies the instant the throttle is released. I have found that I am not getting spark to the front two cylinders. I tested and even swapped the coils around and still no spark to the front two cylinders. I think it may be the CDI box but which one controls the front two cylinders, the red or white plug one? Anyone have any other ideas on what I can check before buying parts? Any help would be greatly appreciated!

 

Since you have eliminated the coil as the culprit, it could be the spark unit (CDI)or the pulse generator. You can test the pulse generator....for cylinders 2 & 4, measure the resistance between the white and blue leads, for 1 & 3, between the white and yellow leads, resistance should be 315 - 385 ohms. Only way to test the spark unit is to replace with one that is known to be good. You might check the spark unit plugs for non-contact, corrosion and/or damage. I don't know offhand about the red and white plugs, I will look at mine tomorrow and let you know.

 

Welcome to the forum Dave. But you gotta post up pix or you will be hunted down. Sorry can't help you with your problem. I am not much of a techy for bikes. Or anything for that matter.

 

Thanks for the help, didn't think of the pulse generators. Where can I find the leads to the pulse generators to test them? I have a book but the old owner was nice enough to not include the wiring diagram. He had also tried a "new" cdi but he said it didnt fix the problem. I'm not sure if the cdi he tried was good or not. Again I much appreciate your time and help electrical problems are not my strongest area.

 

Maybe you can download a copy of the manual with wiring diagram, you will need or want it to trace the wires. Since the previous owner tried a CDI , it does seem that the pulser may be the culprit...

 

I'd be suspect of the ground to the two front coils, black/white I think. For both not firing, it most likely is something in common with both coils

 

According the FSM, the spark unit with the red plug is for cylinders 2 & 4, The 2 front cylinders, #2 on the left, #4 on the right. If you need the wiring diagram for the spark units and coils, I can scan & post it.