Topic: Wiring new aftermarket coils

[kidvid]

I bought aftermarket coils and plug wires because the old ones on my CB500 were cracking and brittle, ends were falling off. Now I've experienced two problems. I bought Accel coils.

First time I wired them, I had a black to each coil, and a yellow to left, a blue to right. Black was on the right terminal. (the Accel instructions had no wiring diagram. I was trying to match original). It blew the fuse when key was turned on.

I swapped terminals, with black now on the left (on each coil) and the colored wire on the left. Now the engine turnes over, but I don't get a spark.

Any ideas?

[Bodi]

Dual fire (two spark plug leads) coils do not have any specific primary polarity. The black 12V ignition power wire can go on either primary terminal, the blue or yellow points wire goes on the other.

So why did it blow a fuse, and why does it not work now?

- What's the primary resistance of the new coils? There are many Accel coils available (for points, for electronic Kettering systems, for CDI systems...) but with stock points you should have 5 ohm coils. Measure the resistance between the primary terminals with a decent ohmmeter. It should be around 5 ohms. You can use 3 ohm coils but your points will burn out relatively quickly, and you may have charging problems. Below 3 ohms... nope.

- Do you now have 12V power at the coil power black wire? Measure voltage. The kill switch may have failed, the new fuse might be bad, a wire connection may have failed. It seems there was an overcurrent situation (it blew the fuse) and this stress can cause already compromised switches or connections to completely fail.

[kidvid]

I went back to the points to make sure I was getting 12v out - and I was. Then I  moved to the coils, and all was good there. I pulled each new plug wire, and checked my crimp job - and didn't find a problem. I then tried it again, and all worked fine. So I'm not sure at all what was causing the fuse to blow. It may remain a mystery - which I don't really like. But it's running with new coils. Thanks for the answer.

[72500john]

as bodi said what is the Resistance of the primary windings of your coils. if less than 5 ohms aka 3 or 2 ohms it will draw too much and be a problem.  dyna makes a coil to fit these bikes. p/n dc8-1 5 ohm replacement.