Can 1/2 a coil go bad?

1978 KZ1000 with point ignition. Got the bike running but it only fires on #2 and #4 at idle the loads up with fuel and runs like junk after 30 seconds or so. Here is what I have tested so far.

1. I have 12 volts to both sides of each coil.

2. Have 12 volts at the points when they are open.

Still no spark at #1 and #3

I am thinking timing but the haynes manual I have is not much help there. Any sugestions?

1/2 a coil go bad? No I don't think so. Do you have it wired so one coil feeds cylinder 1 & 3, and the other feeds 2 & 4?


Have you measured your coils with a meter? The manual tells you how, or else search the Electrical forum here.

Double check the points gap for 1 & 3. The manual should be able to tell you how to time it.

check for resistance across your coils. It sounds like you're getting a weak spark on the two cylinders that are firing, you might also be getting a weak voltage across your spark plugs that aren't firing.
Also...
Look for bad spark plug wires. Swap the wires on the coil terminals (swap 2&3, and then try swapping wires for 1&2) and see if the "missing" cylinder follows.

I thought the coils fired #1/#4 and #2/#3? I measured voltage in and out of the coils and it was 12 volts on both coils.

I think I have it timed right now. It is firing on all four but 2 and 4 seemed hotter at the exhuast. I'm guessing lean, but I probably need to take it for a ride to get things warmed up and burning right. All these tests have been without an air cleaner (which I just got in the mail today) so I will put that in and run it for a while. Can I sync that carbs with one vacuum guage going from carb to carb?

1978KZ wrote:

I thought the coils fired #1/#4 and #2/#3? I measured voltage in and out of the coils and it was 12 volts on both coils.

Yes, 1 & 4 and 2 & 3.

No, you can't have half a coil go bad on a KZ 2 or four cylinder.

And I'm glad to hear you got it running

Ahh, I was mixing up my numbers...:blush: 1-4 and 2-3.

OK time to go ride

1978KZ wrote:

Can I sync that carbs with one vacuum guage going from carb to carb?

Theoretically yes, but in practice very very difficult.

The four slides attach to a common shaft. When you change one, the others change a bit as well so it would be virtually impossible to synchronize four carburetors with one vacuum gauge. In addition, if you are running on two cylinders, have you tried swapping 1 & 4 plug wires and 2 & 3 plug wires? Seems to me that this would pinpoint bad ignition wires, caps and the spark plug on the non-firing cylinder. A coil fires both leads at the same time and can't have one go bad normally. 12VDC in? 12VDC out? How did you accomplish this? You checked voltage with the bike running on the out side at the plug cap? Did I misunderstand?

loudhvx wrote:

1978KZ wrote:

Can I sync that carbs with one vacuum guage going from carb to carb?

Theoretically yes, but in practice very very difficult.

Check the resistance on the coils the input should be 3 or 4 ohms the output should be 23,000. If you have resistance caps check the output with the caps off, while thay are off cut the wires back around a 1/4 inch to get a clean contact area. The voltage should be the same as your battery. Recheck the points make sure the gap is right. Check the timing with a timing light and check the advancer unit.:woohoo:

Here's how I checked the voltage.

1. Key on, there was 12 VDC to each of the input terminals and 12VDC when each of the points would fire.

2. Test light would light on the points when they would be firing.

Here is the strange thing: I grounded the plug on the block and no fire, lifted it away (1/8") and they all would fire. So I think that plugged pilot jets (making the engine seem as it is not firing because of no exhaust heat) and not checking for firing properly led me down this road. I re-cleaned all the pilots and all the exhuasts get equally hot and it seems to idle and rev up well. I thought I was ready to take it for a ride but discovered that I had no brakes. All the lines were dirty and rusted. Cleaned everything and I now have brakes so maybe tommorow when I get the fork seals in I will get it on the road.

The 12 volt check is ok, but are the coils amplifing the 12 volts?