kz 750 won't start

new member here.
I'm trying to help a friend get his bike going. it only had a weak spark on one coil. I tried a set of coils from a known running bike and still only two of the wires made spark. then I switched pickups and nothing. then I swithed IC igniter and nothing. I have no spark at all. I have 12 volts at the coils with the key on. I have continuity through the plugs from the pickups and the igniter. nothing. I put all those parts back on the other bike and have spark. I even swapped out the regulator. nothing. I'm on the verge of damaging a friendship over this bike. any ideas?

You swapped the coils, ignitor, and pickups with ones from a good bike, so that means it's probably the wiring. What kind of condition are the wires and connectors in general?

Measure the voltage on the coils while the engine is turning. When the engine is not turning, there is no current through the coils, so the voltage at the coils won't drop.

Also, what year and model is it?
Does it have an ignition-cut-off switch on the kick stand?

Post edited by: loudhvx, at: 2006/10/04 11:17

My prediction:

It's a bad ground connection to the igniter.

it has a build date of 12-79 E model. the voltage at the coil drops about 4.5 volts when cranking. I get .5 ohms rsistance when testing continuity from the black/yellow wire from the ignitor to the frame. no kick stand switch. is there a way to test pickups?

Post edited by: stanley, at: 2006/10/05 12:25

The ground should be checked against the battery ground. However, a bad ground won't account for the voltage drop at the coil.

The voltage drop at the coil may also be happening at the ignitor, which would probably cause it to malfunction. As a quick test, run a jumper from the battery positive to the coil's positive. (That will also give power to the ignitor.) Then start it. The kill switch and ignition switch won't turn the bike off, so be prepared to disconnect your jumper. If that fixes it, then you have bad connections and/or wires. You can either replace or fix the bad parts, or you can do the Wiredgeorge coil-relay mod as a bypass.

Post edited by: loudhvx, at: 2006/10/06 11:24

with the jumper in place I still get a 3 volt drop. wiredgeorge mod?

There should be almost no voltage drop on that jumper wire.

Put the meter from one end of the jumper to the other while it's connected.
What's that voltage?

Put the meter from the battery's negative to the battery's positive while the jumper is in place.
What's that voltage?

Put the meter from the battery's negative to the positive of the coils while the jumper is in place.
What's that voltage?

The WG coil-mod is the same as that jumper, but it has a relay in the middle to switch the jumper out when the bike is off. There are a few threads on the subject going on right now.

I have a two to three volt drop in all of these conditions. could the ignition switch couse this?