by sportsterpaul » Fri Jan 15, 2016 2:54 pm
I like this much better than "Have your girlfriend hold the plug while you kick, if she jumps, you have spark." I would add the most common problem I have had is condensers. They are filled with electrolyte and will dry out and stop working. Now that they are all aftermarket quality is generally shoddy. Don't be surprised if the brand new condenser stops working or doesn't work at all. Not starting is one failure mode, but I also had a bad condenser that let the bike start, but it could not rev above idle, and would burp and backfire.
Points are pretty reliable, you can just pry them open and look at the contacts. I have only worn one set out in my life, and that was the rubbing block, not the contacts themselves. It is amazing how raspy the contacts can look.
If you leave the ignition on, like the bike stalls as you park it and you forget to turn off the ignition, you will drain the battery sure, but I have also had the coil overheat and split. This is the new plastic type used in the 1970s.
On "cone" motors, the most common failure is the fly-weights egg out and start beating against the back side of the breaker plate. Then the center screw snaps off at the camshaft. Real joy. Happened once to me, at Immigrant Gap, half way between San Jose and Reno. I carry an entire spare mechanical ignition set, even on bikes with electronic ignition. I use anti-seize on the 1/4-24 screw and if you are really lucky, you can walk the broken piece out of the camshaft with a scratch awl.
A big thing is visual inspection. I don't even put the cover plate on the cone motor ignition. I get caught in the rain and the points don't seem to care. For electronic ignition that you put in the cone, I think it is essential to leave the cover plate off so the electronics stays as cool as possible.
The "stand-up" circuit breakers in pre-cone motors are very little trouble. The just seem to work.
If its night you can turn on the headlight and slowly kick to see the points open close. As the load changes there may be a very small change in brightness. Much better to use Erik's method.
I can't help much with magneto bikes-- if they work they work and stay working, there is a reason they use mags in airplanes. My first suspicion is plugs-- make sure the small gap is clear, heck carry a couple spares that are gapped and ready to slap in. After that, I would suspect condenser, if the points look OK, and open and close as you kick the bike over. I did have a carbon track form inside one cap, and a new cap fixed that.
I always wanted to slap a mag into a cone motor gearcase, they make special mags that drive off the tach drive hole. Then I would still run the cone, and have dual-plug heads. Completely redundant ignition, that would be great, like two mags in an airplane.