The Old Prob....

with low voltage at the hot side of the ignition coil primary winding. Yes, I understand from my buddy who hangs here about the relay fix to work around all the voltage drops, etc. Is there another less obvious cure for this problem ??
Apparently this whole voltage drop thing is endemic in mid-late '70's KZ's of ALL sizes.
Having said all that, is there anyone on this board who has actually tracked down what is causing the voltage drop ?? Or is there some tech article I've missed during my poking around the board ??
After messing around with my Fluke 77 for an hour or two this morning on my KZ650C2, I've found that there's about 0.5 VDC drop on the kill switch wire that is routed inside the handle bars. There are smaller drops at various points including the ignition switch.
By the time I got to the hot side of the ignition coils, I'm only seeing ~10.3 VDC instead of full battery voltage.
Is this a case of "resistance stacking" or am I missing something ??? I don't want to fry my coils because good ones are getting quite rare.
Any/all help greatly appreciated.

Don't think you missed anything at all Rick. "Resistance stacking" is exactly the prolem. Those 30 to 40 year old switches and connections all add up to a big voltage drop.
Ride safe.

Thanks for that, Milkman.
Hmmm....I've used spray contact cleaner and dielectric grease on everything I can get at to try to reduce the resistances. I noticed in one post here by someone about how the hot-side wire from the harness through the handlebars to the kill switch can be problematic. I may just pull that harness out and go one gauge heavier on that particular wire. It may be that ALL the wires in that particular circuit need upgrading. Well, we'll see what happens. If I only had more time to spend on this......Grrrr.....

It sounds as if you have a very clear grasp of what's happening. Good stuff!

I tried to reduce the series losses by disassembling and cleaning all the contacts from the battery positive, to the kill switch, to the coils and to the bullet connections in between. The results did not come close to the those of the Relay Power Mod. With only the DPST relay contact losses and the losses of the new additional fuse holder there is not much stopping all of the battery voltage from appearing across the primary of your coil.

I was so impressed that I used the same relay concept to solve my head light voltage problem and later to turn my Headlight off automatically when I press the start button... to save my battery. Sure made a difference.

Remember, the dielectric grease will keep oxidizing moisture and air off your metal contacts but will not directly result in a lower resistance contact. That is accomplished with clean contact surfaces. But, I suspect already know this.

Just one more thing. When I opened up my Kill switch it kind of fell apart and it ended up being a rebuild project. So, if you can get away without opening it all the better. On the other hand you may be looking at it as half the fun of owning a vintage bike. I know I do! Let us know how it turns out with pics if you can.

Best of success! Enjoy the riding season.

I'm trying to win the contest for the most "Double Posts"!

Post edited by: bill_wilcox100, at: 2007/04/30 13:05