No spark - how to troubleshoot

Hi all, bike is a 1980 KZ750 LTD Twin, 14,500 miles. Bike had a failed starter clutch and has been sitting for about 6 months outside.

I just replaced the starter clutch, the engine turns over just fine, but it doesn't fire. I'm using an inductance timing light and its not getting anything on either cylinder. Also, I cannot see any arcs at all at the points (shouldn't I see some little sparks?)

I've already done the coil repowering mod, doesn't seem to matter whether its powered by the relay or as it originally was. I'm running it connected to my car as the battery is weak.

Here's my question - whats the best way to troubleshoot this? If I had something simple bad, say, a spark plug or a spark plug wire, would that prevent the points from showing any life?

I'm trying to get the bike running well enough to be able to sell it so I'm trying not to spend too much money and throw parts at it.

Any suggestions?
Thanks
-J

masospaghetti wrote:

...., I cannot see any arcs at all at the points (shouldn't I see some little sparks?)....

If you have a voltmeter, check the voltage across the ignition points _when they are open_. If you don't have voltage there, then they are not going to do their job.
I wanted to see the electrical schematic to see what the best checks would be to help you track down the trouble, but for a 1980 LTD, the diagram in my manual, which is a Clymer, does not even indicate the points as a component. I am not sure what value this thing actually is. It seems fairly informative till I go looking for something specific, then I seem to come up short most times. Any of you guys have a better manual for my '78 KZ1000A? Or possibly, the 750 really is a lot different from the 900 & 1000.
Where I would expect to find ignition points in the diagram, I do see a "pulser" and a "integrated circuit ignitor unit", both shown in block form, but nothing that actually tells me anything useful.

Post edited by: JimatMilkyWay, at: 2007/02/18 13:09

well, I measured the voltage across the points, and I got 11.6 volts. But I tried measuring the ignition coil...4.8 ohm on the primary (barely in spec), but the secondary had no reading at all. Upon jiggling one of the spark plug wires, I would get an intermittant reading.

I'm going to try replacing the coil and seeing what happens.

masospaghetti wrote:

well, I measured the voltage across the points, and I got 11.6 volts. But I tried measuring the ignition coil...4.8 ohm on the primary (barely in spec), but the secondary had no reading at all. Upon jiggling one of the spark plug wires, I would get an intermittant reading.

I'm going to try replacing the coil and seeing what happens.

Good find Dude:woohoo:
Sorry 'bout the coil, maybe you won't have to replace it. Keep in mind if you do, however that a few extra thousand volts for the old sparkers never hurt any off the line acceleration neither.
You know, I forgot to mention something. If you do, in fact decide to keep the old, outdated breaker points, you need to be sure and clean the contacts. Would you believe that you could still read close to 12VDC across the points even with them _closed_? What that would tell you is that the contacts are dirty and therefore not closing electrically. They might be closed mechanically and you would not know why you gots no sparky.:whistle:

Thx for the reply!

I measured the voltage when the points were closed; 0.09 volts. I definitely would upgrade to a electronic ignition if this were a long term project but i'm really just trying to get rid of the thing...

masospaghetti wrote:

Thx for the reply!

I measured the voltage when the points were closed; 0.09 volts. I definitely would upgrade to a electronic ignition if this were a long term project but i'm really just trying to get rid of the thing...

90mV, or millivolt readings in general are not really entirely reliable, IMHO unless you are very certain of 1) your equipment accuracy and 2) the location of contact points you use to do the test. I am not talking about the ignition contact points, but the physical contact points for the meter leads.
So what's next? Do you replace parts or do you get coils off FleaBay or order stock from Z1enterprises for example.

Would one coil from a 4-cylinder KZ700 work? I have two stock ones sitting around because they were replaced with Dyna coils.

masospaghetti wrote:

Would one coil from a 4-cylinder KZ700 work? I have two stock ones sitting around because they were replaced with Dyna coils.

Don't mix coils.

masospaghetti wrote:

Would one coil from a 4-cylinder KZ700 work? I have two stock ones sitting around because they were replaced with Dyna coils.

You can use a single wasted spark coil on a parallel twin with dual breakers on the camshaft, provided the primary resistance is the same as what you are replacing. You'll have to parallel your points. Points will not last as long if you've substituted a lower resistance coil.

-Duck

If the KZ700 coil measures 4 ohms it should work. If it measures less than 3 ohms, you'll need a resistor to make up the difference. 1 ohm, 25 or 50 watts.

(There's only one coil and one set of points on the twin's crank. It's 1/2 of an inline four. Later, smaller KZ twins had non-360 cranks and may have two single-output coils.)

Post edited by: loudhvx, at: 2007/02/21 23:09

Duck wrote:
You can use a single wasted spark coil on a parallel twin with dual breakers on the camshaft, provided the primary resistance is the same as what you are replacing. You'll have to parallel your points. Points will not last as long if you've substituted a lower resistance coil.

-Duck[/quote]

Am I just endangering my points? My KZ700's coil measures just over 3 ohms.

I just got the bike running, though! The old coil was definitely shot, the points had a huge layer of filth on them, the carbs were gunked, the spark plugs were bad, the wires were bad, and the battery was bad. And the starter clutch was also bad.

The bike, for now, runs like a champ, except that I managed to get a nail in the tire.