KLF300C 1991 misfiring. Tried everything, out of ideas -ish.

[MaxPax]

Backstory: ATV Ran fine, once stopped in the forest and had to be towed back to my workshop. Found that the stator connector was melted together. Fixed that and it ran mostly fine but intermittently lost spark. Changed CDI box which fixed that problem. Ran fine for a year, but started to misfire more and more often until it did that most of the time. It's not really losing spark, it's firing when it's not supposed to, occasionally making the engine kick in the wrong direction if the revs are low enough. I found that disconnecting the charge regulator would make the problem disappear. I measured the regulator, one diode seemed bad so I got a new one. No change. I then bought another new CDI box and changed the stator and ignition sensor as well as the ignition coil to make sure everything in the ignition circuit was new.

And now, it's still doing it. I'm leaning to a broken cable/connector somewhere but it seems illogical to me that it would spark when not supposed to if it were that. Any suggestions is very much appreciated!

[Savage3]

Did you verify timing on flywheel?

[spock58]

It's possible that the flywheel key has been damaged which lets the ignition timing get messed up.

You'll need a puller to remove & inspect those parts.

[MaxPax]

Even though the problem completely disappears when I disconnect the charge regulator?, maybe I was unclear, that is still the case. Bike runs fine with it disconnected but does not charge the battery at all obviously. If it would be the flywheel key that is compromised, I believe it would still be running wonky without the charge regulator...

Edited May 2, 2021 by MaxPax

[Savage3]

Great point sir. Sorry, I missed that it ran perfect when regulator was disconnected. Is there 4 wires connected to the regulator? Two going to stator, one going to ground,  and one going to the battery?

[Savage3]

If there are 6 wires, check the brown wire going to engine stop switch for damage causing a short to ground. Oftentimes, wires have been hacked and the colors may vary.

[Savage3]

When testing voltage at battery while running, is the regulator providing about 14.5 volts at 2000 rpms?....(approximate)

[MaxPax]

Thank you for your suggestions, sir. I will check later today when I come home from work. The regulator have six wires.

[Savage3]

https://pin.it/4Qc8r5b

This diagram may be helpful sir.

 

Edited May 3, 2021 by Savage3

[Savage3]

I realize the schematic is 1988, I believe the 91 is the same. (Not positive, going off memory) If not, you will know immediately after viewing. It sounds based on your description, that one of the wires coming out of the regulator is shorting to ground. Possibly, the regulator itself has a bad diode as well. Difficult to diagnose without being able to test. I'm hoping these ideas will in some way direct you to the problem. Many times, if voltage is less then 14.5 at the battery with engine running at about half throttle, the rectifier is bad. Not 100 percent, could also be a wire short circuit in the mix.

[MaxPax]

I checked, the brown wire was indeed shorted to ground. I pulled it out of the connector and the few minutes I let the bike running it seemed to run just fine. Before though, after changing the cdi box and stator, it seemed to run fine for about a day until it wonked out, so I am excited but a bit reserved about this. However, it's charging 14,5 volts on idle and 14,55 volts with half throttle.

You sir might just deserve a bunch of free pizzas, if it stays fine now I will be a happy man with some extra parts laying around, like a fully working stator assembly haha.

Question now, can I leave the brown wire out? The reverse light works and the stop switch works, seems there would be a reason for that wire to be there. Can it be disconnected without causing other problems down the line? Maybe the wisest thing to do is to find out where it grounds and fix it...

[Savage3]

I'm at work now sir....I'll get back to you. I believe it goes to the kill switch. If engine shuts off with wire disconnected, you may be ok ( may be a redundant ground for safety).....I'll take a peak at wiring diagram this evening.

[Savage3]

Check ALL lights, make sure there are no issues. I'm a bit sceptical as well.

The problem could also be in the ignition switch. (The switch is on same circuit)

Sometimes, the ignition switch contacts get rusted and results in fluctuating voltage. Kawasaki's are not happy when the voltage/current is not perfect!

However, since the regulator is testing perfect, I'm assuming the ignition switch is not causing issues. Therefore,  it appears the issue is isolated to the wire shorting to ground.