1983 KZ 750 L3 running on 2 cylinders

Hey all,

Problem: My bike is running on 2 cylinders.

Background: I bought this bike in a rough state in 2020 and have slowly been putting it back together. One of the first problems I fixed was the bike jumping between running on 2 cylinders and the full 4. When I bought it the wiring was a mess, with lots of melted coatings and wires that were just in brutal shape. On top of that there was white fluff (oxidization?) all around the battery that I assumed was a battery overflow. It had dripped down over much of the wiring and relays but I managed to clean it up. I got the bike running on 4 cylinders back then by replacing the broken wire and shrink wrapping exposed/vulnerable bits. I planned to replace the ignition coils but the bike ran well after the wiring was cleaned up so I didn't bother. Long story short he motor has been running great…..until a few days ago.  I was surprised on a ride two days ago when the old problem came back. I shut the bike off and restarted it which got me back home, but yesterday I started it up and it won't run on 4 anymore. 

Potential problem locations: I'm thinking the problem could be a few things. I'm very new to working on things so you'll have to excuse any ignorance. When I opened the bike up I was surprised to find a bunch of the white fluff (oxidization?) had reappeared under my paint (Pic #1).  I'm thinking this has to be electrical because I stripped and painted all the internal metal electrical holsters less than 7 months ago.


My first guess was that the relay was gone (pic #2)
 
but then I noticed that my positive battery hookup (the main power source) had lost its jacket and was exposed (pic #3),

so perhaps it was hitting the frame and shorting something?

Conclusion: I'm at a loss as to why my bike is running on 2 cylinders but I know something is up with the electrical. Any insight would be appreciated!


Thanks,
Mitch
 

The white stuff is sulfur dioxide and it´s very etchy, (boiled overload battery). Give all electical parts in the area like, connectors, plugs, wiring bullet and spat connectors a good clean with a brass brush and WD40. Unplug all connectors to look closer for oxidations that create restiction to the power flow. In worst case you have to pinout the connertors to get a better access for cleaning.

The thing is I don't see any battery spillage like drips from the battery itself. The white stuff seems to be coming from inside the metal (under the paint.) 

Are you suggesting that corrosion at a connector is limiting flow and causing my problems?

Any Idea on why it's running on only 2 cylinders now?

Thanks for your reply,
Mitch

Which two are not firing? If it is 1 & 4 OR 2 & 3, then maybe a coil problem, or a wiring problem going to the coil.
 

The relay in pic 2 looks like hazard (4 way flasher) relay. Mine has 2 orange green wires. Unlikely to be the cause of problem.

 

You have several problems that may or may not be related.
1. Corrosion. You are probably right that the corrosion in the first picture was caused by battery acid. It came back because it was not completely removed and neutralized the first time. I think the best way to save the battery box will be to completely remove it, strip the paint, soak it in a strong baking soda solution and scrub it with a brush. Fiercely. When you are sure every spec of corrosion is gone, rinse it with clean water, dry it quickly and apply a good primer. When that is properly dry, apply several light coats of high quality paint.
Take a shop vac to the rest of the corrosion in the bike. Use a fairly soft brush to knock loose as much as you can while vacuuming. Once the loose stuff is gone, you can make a paste of baking soda and water and use a toothbrush to vigorously brush the remaining corrosion, then carefully rinse with cold water and blow dry.
2. Corrosion on wiring connectors. I am not a fan of WD40. I much prefer a dedicated electrical contact cleaner like Deoxit D5. If, however, the corrosion has invaded the wiring, you may have a major problem that could necessitate replacing the wiring harness. Look carefully at the wires that have corroded connectors. If you see any lumps in the wire near the connectors, corrosion has likely attacked the wire.
3. Battery terminal cover. It is not really needed as long as the battery is properly tied down and you do not do something silly like touch it and the frame at the same time with a wrench or screwdriver. The battery really needs to be properly tied down for its own health and your safety. If the battery has not been tied down, it could be splashing acid all over the place while you ride. When it is time to replace the battery, I suggest an AGM. They are sealed and a good one will last many years.
4. Two cylinders dropping out. There are several possibilities including a cracked coil, old secondary wiring that is arcing to ground, an intermittent problem in the primary coil wiring from the igniter ot to ground.

Thank you for the Replies!
I've been very busy lately so haven't been able to respond sooner/give the bike much attention. 

Interesting on the battery acid. I thought I had cleaned it off well enough before I primed and Painted it but the baking soda solution is a new idea, I'll try that and repaint.

The battery is always tied down when riding, I Just took the harnesses off for pictures/investigating.

I'll look at the wires, maybe replace the ignition coils and post an update when/if I find a solution. 

Thanks again for the help,
Mitch

Have you check the wiring under the tank? Specially the wires that's going to the coils?

I had a similar problem with my 82 when I was riding it. While riding, without any trace, engine would go from all four to two. What was happening was the harness right below the tank sometimes gets trapped between the frame and the tank and was causing a short. Since then, I fixed that problem and never had it again. But I had to pretty much unwind the whole harness to get to and find the problem.

I'm not sure you're having the same thing, but just my experience.