No spark stump the chump

missionkz wrote: Pull the plug wire from the coil in question and put a screw driver into the boot.
Turn the engine over by hand until that coil's points are closed.
Use a small blade screwdriver at those same points to push them open and closed.
Turn the ignition on and hold the screwdriver which is stuffed in the plug boot, by its handle so you could see an arc from the screwdriver to engine/frame ground when you open and close those points.
If it fires a nice spark I think your coil is ok.
A good healthy battery and coil should be able to throw 1/4" to 3/8" long spark.

This seems like basically the same test missionkz suggested. I ran his version and got a spark when I lifted the ground. Plugs seem to be sparking, but so are the points.

So I shouldn't see any sparking between the points?

Have you checked timing?

Can't really check timing until I can get it running.

You can do it by making the points open when they just come to the F mark. It's rough but will work.
Steve

I doubt it's timing, but I'll check that when I get home. Bike was running well when parked about a month ago. It sat for a few weeks and then wouldn't start. I doubt timing could get off in that scenario. But like I said, I'm stumped. It seemed reasonable that the condenser could fail and it apparently had.

I'm most concerned about the visible spark jumping the points. I know I've seen that before on the bike and figured it was normal, because everything else was going fine. But based on the comments in this post and what I see in my manual I gather that's not normal.

I'll have to wait a few days until the new set of points arrives to see if swapping those out has any effect.

You can use a points or finger nail file. I use a folded match book to clean them. Could be just oil or grit.
Steve

I'm most concerned about the visible spark jumping the points.

The condenser is there to prevent arcing at the points, if working right.

He replaced them. :S I used two early Ford condensers up stream when I was having the same problem. $5 a piece a AZ. Could there be A/C in the system caused by a bad rectifier?
Steve

As I remember it, I was boiling the batteries and got a used regulator from a dead Z1. Always had a strange miss. I parked it in 98 and put in a modern R/R unit this time around. I figured I had a bad diode in the rectifier.
Steve

Boil over from a bad rec/reg will increase voltage from the battery to the coils when running and fry a condenser and points (and other things). Equally if a 4 Ohm coil specification is reading 2 Ohms, more juice is getting to the condensers and points and causing them to fry.

Have you tested coils (primary and secondary), caps, plugs and condensers for spec operating range? And if you get it started get a voltage read on the battery, the rec/reg will keep it under a certain number (around 15 or less volts), If it climbs the rec/reg needs to be replaced. If it drops you may have a stator problem.

Timing, only because I just went through a similar diagnosis and it was the last thing I checked - should have been the first. I'm sure you can run a search for "static timing method" here and find the process without running the engine.

Good luck - you will get there.

Crap, I had a point bloc loosen up on me while I was racing a cute blond 30 years ago. I pulled over, set it by eye and went on my way.
The blond turned out to be breeder and put out 5 kids in so many years. :ohmy:
Dodged a bullet on that one. :whistle:
Steve

Quick update. Still waiting on my points but managed to get the bike started today. Running strong but the points are still sparking.

I just noticed that the new condenser I installed is the wrong part number. It's the condenser for a '76-'77 KZ750. The '78-'79 had a different part number. (Mine's a '79).

Could that be the problem with the points arcing? The lead for the new condenser was too short, so I spliced in a little extra wire for it to reach. Any way to know whether the condenser itself was different for '78-'79 or if the part change was just the lead length?

I'll get the proper condenser just to be sure. I'm just wondering if that could explain the arcing or if there's something else going on.