Introduction: Troubleshooting/repairing a Kawasaki Bayou KLF300 ATV Electrical Charging System

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About: My daytime job Quality and Training Analyst for a Control Systems Integrator. When I am not inspecting Electrical Panels and miles of wiring and control circuits, I like tinkering with all types of mechanical…
These bikes are cool and virtually bullet proof. I have always been around machinery all my life and have always owned some type of ride on equipment, from 3 wheelers, dirt bikes, trail bikes, mopeds, road bikes, tractors, etc, etc, etc.

My issue with the KLF300 was 2 fold. First, it was over charging the battery. Second, it had a strange knocking noise on the engine when accelerating.

A brief history of my KLF300. The old guy next to me bought it new in 1995. He rode up and down the fence lines between our properties on it and pulled a little wagon behind it. That was it. When he got too old to throw his leg over the seat, he parked it behind one of his barns and bought a electric golf cart to buzz around on. It sat there for 4 years with a tank full of ethanol and the fuel petcock left open. He died a couple of years ago and the family auctioned off a bunch of his stuff, including the forgotten about ATV. I knew the history of the ATV, so I put a lowball bid on it and bought it for a song and dance. I went and got my tractor, picked it up with the front end loader and took it home to my shop. It had 4 dry rotted tires, a dry rotted seat, years of dirt built up on it, a gas tank full of dried up ethanol and a carburetor full off dried up, varnished fuel. Ohhh, got my work cut out for me!

Step 1: Rebuilding the ATV

First thing I did was I bought a Clymer maintenance manual. (Invaluable reference) I spent the next couple of weeks tearing the ATV down, cleaning, replacing and rebuilding the various parts of the fuel system. I did a engine compression test. I adjusted valve clearances. I changed the spark plug. I had 4 new tires put on it. I put a new battery in it. I did a custom duct tape seat repair job. :) I removed all of the body panels, pressure washed the engine, the frame, the drive train, body panels and then put it all back together. I put fresh gasoline in the ATV and pushed the start button. Dang it if it didn't pop right off and run! I let it warm up and then shut it off, changed the engine oil and checked for leaks. Life was good. I did notice while it was running that the head lights didn't work and only one bulb in the tail light worked.

Step 2: Huh.......the Glass Light Bulbs Literally Had Melted...............

Now, that is some major heat. Looked like the voltage regulator had quit working. It was putting out in excess of 17 VDC. I replaced all of the light bulbs and replaced the voltage regulator/rectifier with a brand new one from Kawasaki (Kawasaki part number 21066-1089) .

Now, when you go to get electrical parts from the Kawasaki dealership, remember they get real, real proud of their prices for these parts. You see, these parts are coated in invisible GOLD.$185.41

I put the new regulator on and started the ATV. All seemed to be good...........for a week or so. I stated noticing the head lights dimming and getting really bright while riding it at night and the engine started getting a knock in it that sounded like a piston skirt smacking the side of the cylinder on the right hand side when the lights got bright. Wait.........what????

Step 3: Time to Do Some Serious Research and Electrical Troubleshooting

I was beginning to think my ATV that I had just sunk about a grand into it rebuilding it was a real lemon. The regulator/rectifier is located on the left hand side of the air filter housing. Pretty easy to get to it. 1 bolt removes it. I took my Clymer manual and found the schematic for my year and model and traced down every single wire. I broke every electrical connection, cleaned it and made sure the wire connectors and connecting points made good, firm connections. I would start up the ATV, with my digital meters attached to the battery and different check points, looking for a bad electrical connection. Sometimes my meters gave strange voltage readings. I then checked all of the frame grounds, cleaned and reseated them. Sometime the regulator would work, sometimes it would let full power into the battery. More reading. I scoured all the Kawasaki internet sites. What can be causing this voltage/mechanical noise problem?

Step 4: OH......Bingo.....I Think I Found the Problem/s

After a few weeks of riding/testing and troubleshooting, I finally boiled out all of the water in the battery and cooked it. I went and parked it in my shop for the rest of the winter, as it was getting too cold to be bending 20 year old wire in wiring harnesses looking for electrical issues. Now that Spring is here, I went back out into the shop and started looking at the KLF300 again. Battery is DOA. Went and bought a new one. Installed battery. Started ATV. Running like crap and the neutral light is blinking on and off in time with the engine idle. Time for more meter readings. This time, Instead of using my Fluke 87 digital meter, I used my trusty old Simpson Analog meter. What I saw amazed me. My voltage coming out of the ignition switch was wildly fluctuating between 0VDC and 17 VDC in time with the engine idle. I put the Fluke meter back on the same circuit. The digital sampling of the Fluke can't match with what the Simpson Analog meter can do. With the Simpson, you can see the voltage fluctuating. The Fluke can't refresh that quick.

Step 5: Here Is How I Diagnosed/fixed This Common Problem

#1 problem found: The Ignition key switch was bad. With the ATV being left out in the weather elements for basically 19 years, water/dirt got into the ignition key switch, caused undue resistance and the contacts inside severely pitted. The moisture trapped inside rusted out a tension spring and ball unit inside the switch housing that keeps the contacts tensioned against each other. When the contacts are not tight against each other, they start to arc and start to pit, causing voltage fluctuation in the electrical system. This is what I found when I tore the switch apart. I tried to clean up the contacts, but they were way too damaged to salvage. I called Kawasaki for a replacement ignition switch. $100.00. Really??? $100.00 for a 2 wire, 2 position 30 amp key switch? Being that my ignition keys don't have to say "Kawasaki" on them for me to ride the ATV, I took off to my local auto parts store to see what I could find as a cheap replacement. Hello Auto Zone. I found a 30 amp, 2 position ignition switch that comes with 4 keys for $12.00. New switch installed, I start up the ATV. Now, the Neutral light is glowing solid while the ATV is idling. I check the voltage with the Simpson analog meter and the voltage is stable..........at 17VDC. Way too much voltage going back to the battery. I should not be reading anything more that 14.5 VDC at full throttle. It appears that the wild voltage fluctuations coming from the ignition switch caused my regulator to burn out, which is once again allowing full voltage into the battery.

#2 problem found: In reading a bunch of sites, I found one Kawasaki service manager that wrote a article about the KLF300 having a weird knocking noise that sounded like piston skirt slap on the right hand side of the engine. He said before you tear the engine down looking for a pile of metallic shavings inside the engine, do one simple check: Check your voltage regulator. Yep, you read that right. Check your voltage. It appears that on the KLF300s and other systems similar to them, that when the voltage regulator goes out and your voltage is unregulated and high (above 14.5 VDC) , it causes the Solid State Ignition to advance the timing and the knocking noise you are hearing is actually pre-detonation. I tested that theory out by simply removing the regulator/rectifier from the charging circuit while the engine is running. The voltage drops back down to 12.5 VDC on the battery and the rest of the electrical system. The KLF300 engine went from clanking, missing and popping like a old jalopy to purring like a big ol happy kitten once the overvoltage was removed.

Step 6: Checking Out the Rectifier/Regulator

When unplugging the regulator from the harness plug, you will notice that the harness plug has 6 wires in it. The 3 yellow wires on the bottom are AC 3 phase. The voltage coming from each phase should be somewhere between 24-32 VAC. The rectifier part of the Regulator/Rectifier converts the 3 phase AC power coming from the stator into DC. The regulator part of the device monitors the DC voltage of the battery and will either allow voltage back into the charging system if it determines the battery voltage level is getting low or the regulator will shut off the supply of voltage to the battery and will dissipate the electrical power being created by turning it into heat, which is then dissipated into the air via the heat sinks on the Regulator/Rectifier.

The top center pin is the voltage monitor pin. If you consult the schematics, you will see that the regulator is monitoring voltage coming back from the ignition switch. If that ignition switch is not making good contact and the voltage is rapid firing on and off, it will burn up the Regulator/rectifier, as it was not designed to switch the DC power at a quick cycle rate. The top left pin is the battery pin. This voltage is sent from the regulator directly to the battery via this pin. The top right pin is the DC ground terminal pin.

Step 7: So, in Closing, Let's Re-visit What I Have Found:

  1. Get a good maintenance manual.
  2. Check your ignition switch for wear and pitting using a analog voltage meter
  3. Check & clean every electrical connection in your harness for bad connectivity. Don't forget your chassis grounds. Use dielectric grease to seal all connections from corrosion.
  4. Make sure your battery is good.
  5. Make sure your voltage regulator is not over-charging your electrical system, burning up your battery, melting your headlights and causing your engine to pre-detonate.
  6. Don't always assume that the over-priced dealer parts are a superior quality compared to what you can purchase other places for much less $$$. Dealer ignition switch price: $100.00 My purchase price at auto parts store: $12.00. Dealer price for Voltage regulator/rectifier: $187.00. My purchase price online for a new identical regulator/rectifier: $15.00.