Cylinders 2&3 = No Go

First off, before anyone complain, I DID use the search feature.


2&3 are not firing. Heres my case, though. When the bike did not start for me yesturday (which was my first try in 18 years, after the rebuild), I decided to start out by checking the coils. Well, coil pack 1&4 both worked, so I'm good there. When I took coil pack 2&3 out, only ONE spark plug fired (can't remember which). So, 3 of the 4 plugs were firing. BUT, when I finally got it started today (BTW, these bikes sound AWESOME!!!!), I noticed 2&3 are not running- at all.

Now, using the search, I came to the conclusion that it could be the carbs, which in my case, it is not. They were just all cleaned and rebuild, and they are getting gas. Since it is not the carbs, does this eliminate it down to the coil?

FWIW, when REINSTALLING the coil pack 2&3, I felt a STRONG magnetic pull, along with a mix of 'humming/light vibration' coming from that pack (like powerlines, you can HEAR the electricity).

My checklist:

+ Bike has compression on all 4 cylinders
+ Bike gets fuel in all 4 carbs
+ Spark plugs 2&3 appear brand new, even after running the motor for minutes
+ When I take the plugs out, I see that cylinders 2&3 have fuel on the piston

Still have the points ignition,Erik,or is it electronic?

Still the points

Have You checked THEM,and the condensers?

Hi cuddies,
Your bike has two ignition systems, very nearly separate from each other. One coil fires 1&4 and the other fires 2&3. It's not possible to have spark at #2 and not at #3. The only options are neither or both. I'd start by confirming your primary resistance. You should find something near 3 ohms. Next check the voltage to the coils sometimes the connections can be deteriorated and not allow a full 12 volts to get to the coils. If so get a small wire brush and some CR-56 contact cleaner. Do you have a manual? if not get one. I think there's a thread here on KZR where you may even be able to download one.

I don't subscribe to the relay coil power fix, it's easier to just clean the connections. IMHO!

KZCSI

KZCSI wrote:

It's not possible to have spark at #2 and not at #3. The only options are neither or both.

Well, when I bench tested it, I put a plug in number 2, and it sparked when given powerl put the plug in number 3, and there was not spark from the plug. I don't remember which one sparked and which one did not, those number up there may be mixed around. Either way, one fired, one did not.

And I am obviously assuming that 1&4 are fine, because those cylinders are running hot. Would these motors really run on only two cylinders?

Yes I have a manual, I downloaded it from this website.

I have not checked the points or condensers yet; but if I am getting a spark from 1&4, wouldn't 2&3 be getting power, too?

Post edited by: cuddies, at: 2007/05/29 01:34

Leave the carbs alone, for now.
You definitely have an electrical problem.

First, you could have a bad 2/3 coil, with one plug firing, and not the other. There are dual output windings with a single primary circuit. One of the secondary circuits could have failed.

You mention the coil being live when you hooked it up. That is not normal. Why is a coil 'hot' when turned off? That could have burned out part of the coil. That means you could have a bad coil, AND a wiring issue causing it to be "ON" when not selected on.

You could have a bad plug wire.

Want to troubleshoot your points? Swap the coil primary wires between 1/4 and 2/3. If you get the same coil misfiring it is not the points causing it. Back to bad coil or plug wire.
If the problem goes to the other coil it is in the points or wiring.

Don't forget to put it back to stock connections after testing. It won't run that way.

Let us know what that does and we can go from there.

This is a wasted spark system and the coil must fire through both plugs or have one side of the HT winding grounded to fire at all...unless it is defective.

Repeat...When testing your coil, you must have a plug connected to both sides OR ground one side while testing the other.

Since coils don't go bad nearly as often as points give problems, I'd check the points and condensor first.

-Duck

Duck's got it right. The secondary winding has two ends, one connected to each high tension tower or post if you will. When the primary winding shuts down the field collapses and a current is induced in the secondary it flows out of one tower and back into the other tower jumping two sparks in the process. If you're getting a spark in only one plug you're still getting some connection somehow in the other wire. It can't work any other way. By the way you need to be sure that you have a plug in each cap when you're testing these coils and the plugs need to be grounded to something, each other will work fine.

KZCSI

I just had to replace the coils on my KZ550C. 1-4 worked fine, until it got hot, and 2-3 did not work at all. Both coils were cracked on the bottom. I ended up getting some used on ebay for 40.00 and the bike runs great now.

Also check your spark plug caps and also check the ends of the coil wires for corrosion. If the wires are green, trim them just enough to remove the corroded section. BE CAREFUL TO NOT SHORTEN THEM TOO MUCH.

You should have 5 - 10 K resistance on the plug caps.

Test the coils for resistance with an ohm meter.

Post edited by: larrycavan, at: 2007/05/29 22:06

I didn't have much time to work on the bike yesturday, but I did pull the points cover off and took a look. The point probe things had a bit of corrosion on them, so I cleaned them up a bit. Didn't make any differnce, still only runs on two cylinders.