No spark from mag

When first started last spring after the engine rebuild, she fired and ran on the third pull of the crank, so the setup and timing have been good. She's run plenty since, though a few times she took a while to start (with the starter). I'd chalked that up to carburetion, but maybe not. Over the winter, the last few starts have been a matter of her firing maybe ten turns weakly, dying, and retarting only after some serious time on the starter.

I've had the mag off and back on twice today, after she wouldn't start at all. First time, changed out the condensor, touched up and checked the gap on the points. Second round, double checked the points, put yet another condensor in. I pulled the coil off to get a better look at the wire where it passes through to the points. It looks good and I had no continuity from the arm on the points to ground. I'm thinkin' it might relate to condenation (it livess in an unheated garage) as there was a film of rust I don't remember on the magnets, and on the rotor that becomes visible under the coil. Cleaned those up.

Still no spark to the center wire coming from the cover of the mag. The rotor in the cap is on.

Any thoughts? More things or ways to check it out?

You need to clean the points with a piece of 320 wet or dry until they're shiny. If they're pitted replace them and set the gap at .013".

An easy way to keep the mag in time is to note where the rotor is pointing before you pull the mag. It's best to make a little sketch, THEN DON'T MOVE THE ENGINE. To reinstall the mag just put the rotor in the postition shown in your sketch. The applies to a distributor too. Your coil may be ok and if the magnets are weak you won't have any spark or a very weak spark since the magnets are what creates the fire in a mag as they pass by the coil. You can check them for magnetism by touching them with a flatblade screwdriver. They should attract that screwdriver
with a lot of effort. Here's a mag off an old twin cylinder garden tractor with weak magnets.
Hal

Could be weak spark, I suppose, but for the moment I'm gonna chalk this one up to dampness.

I don't know much about magnets, but I wouldn't think they'd go weak in a hurry, and I don't know if they work better when they warm up.

There was a lot of surfaace rust on the magnets from condensation that I cleaned up when I had her open last night. I'm thinkin' that might have cleaned itself up a little.

I left her run until she was warmed up, if only to get the battery charged back up after all the crankin' I did yesterday, and she was runnin' right when I shut her down a few minutes ago.

I'm gonna try runnin' it on a daily basis for the next week or so to see if it's gonna stay straightened out or if I'm gonna have to do somethin' else to get it right.

Paul

• Mag Manual

If it's the one I'm thinking of, I've seen that and thought I had a link to it, but couldn't find it. Either I didn't grab it, or it saved as something I can't identify it among my (too) many bookmarks.

Your link posted as just text, though (no link). Can I ask you to give it another try?

Sure appreciate it!

Paul

• Mag manual

Any idea where the continuity should be on that coil? Across the two threaded ends or between one of those ends and the wire that runs to the head of the condensor?

I'm kickin' myself a little. I did think about the magnets both times I had it open. Not that I'd know a strong one from a weak one, but I thought and then forgot to see if they'd grab a nail I had on the bench and hold it.

Thanks!

But I'll put the analytical skills back to it tomorrow so that, with any luck, I can nail the problem down and get on the horn Monday to get what I need to get her fixed. MagMan'll be the first call.

I'm thinkin' while I'm at it, I need to eliminate a bad contact in the cover. Also gonna try checkin' for continuity to ground at the ground post (with the wire to the switch disconnected) while turnin' the engine by hand. Thinkin' that I should have continuity there when the points are closed, and lose it when the points open. If that's the case, I can eliminate a short in the wire from the points to the condensor. That'll pretty much leave the coil and magnet, or something affecting them.

Not sure that'll work 'cause the ends of the coil body are smack up against the magnets, so I'm not sure how or if it's isolated from ground, though it seems it would have to be. I'll just keep approachin' it as a learnin' experience.

Appreciate your help!

Nope, I had the switch up and at one point, never even hooked up the ground wire back to the switch, figurin' I could touch it to and shut her down if everything went right.

Always worth askin', though, given my record. ;8^)