TOPIC:

A little background. My 77 KZ650 had a leak on carb #2. The bowl and overflow tube were constantly wet. I removed all the bowls and found dirt in all of them that I cleaned out. It seemed to fix the leak, but now the bike has a rough spot around 4000 RPMs. I figured that the needles are now sealing properly, resulting in the fuel level in the carbs being a little lower, resulting in leaner running. OK. Not a big problem. It still runs decent. Then it started blowing the main fuse. After it blew the first one, it blew two more before I could get it out of the driveway. I tracked a short down to the regulator. After disassembling the regulator, I decided that it wasn't the problem, and that it was just providing a path to something else that was causing the short. I put it all back together and the short was gone. Great. It went about 9 miles and then blew the main fuse again. This time the blown fuse and the fusebox showed signs of excessive heat at one contact. I then found that the clip on that end of the fuse was not clamping firmly onto the fuse. I then decided to go through the whole bike and recondition all the connections. This included Dremeling any contact I could, squeezing the ends of the connectors to increase contact pressure, and applying dielectric grease to all connectors. The bike ran worse than ever. Sounded like it was running on 2 or 3 cylinders. I tried to ride it to work, but I had to turn around after a couple of miles. I found that spark plug 3 was not getting spark. I also discovered that I never replaced the plugs during the initial restoration as I'd planned. The plugs were 10+ yrs old and rusty. OK, they need replacing. But that doesn't explain why cyl 3 picked this time to stop firing. If anything it should be getting better power, not worse. So I replaced the plugs, and now I have spark on all cylinders. It now runs on all cylinders, but the rough spot at 4000 RPMs is still there and it's worse than before. After it completely warms up, you can get it to rev past 5000, but not before. After it gets to 6000, it pulls great up to 8000 which is as far as I pushed it. Since it pulls great to 8000, this should mean that the ignition is getting plenty of power, and the carbs are getting plenty of fuel. Right?

So, do I have an electrical problem or a carb problem? Why did refurbishing the connectors cause cyl 3 to lose spark? Dielectric grease is not supposed to improve or degrage the integrity of a contact. It's supposed to prevent oxidation, which makes a good connection last longer. It shouldn't cause a cyl to lose spark. And why is the rough spot worse than before? This weekend I plan on replacing the fusebox with a blade type fuse block. It has 4 slots, and I plan on using the extra slot (in the future) for Wiredgeorge's coil repowering mod. One of the results of this mod is to improve ignition when the mixture is lean. If the above symptoms point to a particular problem, I'd like to fix that and not have the coil power mod cover it up.

If using points ignition, would clean, then gap, and then set ignition timing.

Next -- check primary and secondary ohm readings on coils. And are plug wires and caps in good condition? And how old are they? Try water spray over plug wires and caps at night in pitch black garage with engine running. A free fireworks show indicates leakage between coil and plugs -- often old plug wires.

Next -- assure correct valve clearances.

The above being recommended before getting to carbs (because carb function so heavily depends on correct ignition and compression components).

When last resorting to the carbs, would first check the service float bowl fuel level using the quick easy clear plastic tube test.

Pretty sure the ignition problems aren't due to any of the carb work.

Good luck with eliminating the rough spot.

Another thought --
When cleaning the float bowls, were the bleed pipes, main jets, and pilot jets also removed and cleaned?
All air passages clear?

Just checking

I found it. Short answer: the problem was electrical.

Long answer: I replaced the fusebox with a blade type fuse block, and I performed Wiredgeorge's coil power mod, and now the bike runs MUCH better, as well as the electical behavior of the bike is much improved. I wanted to see how much improvement each change made so I measured voltages before and after. At first I tried to measure voltages at the battery and at the coils, but the battery voltage drops when you turn on the ignition switch. So instead I decided to measure the voltage drop from the battery positive terminal to the coils. With the original fusebox, the voltage drop was 2.0 volts. I don't know if that's bad or not, but it seems like a lot to me. After installing the new fuse block, the voltage drop was 1.35 volts. I didn't expect an improvement of 0.65 volts, especially since I had previously cleaned up the contacts on the original fusebox. The bike ran MUCH better. It seemed to have all the benefits everyone claims for the coil power mod: better cold running, better idle, smoother acceleration, etc. In addition, the blinkers flashed faster. So, if improving the voltage to the coils by 0.65 makes that much difference, the coil power mod should REALLY make an improvement. After the coil power mod, the voltage drop to the coils was 0.09 volts. OK, this should work great, right? Well, I couldn't really tell any difference in how it ran. If there was a difference it was minor. If I had it to do all over again, I don't know if I'd do the coil power mod, but I'd definately do the fuse block mod. I'm not going to undo the coil power mod, but if anything on it fails, I'll remove it. Having said that, I'm really happy with the way the bike runs when cold, and how it idles when cold or hot. After doing the coil power mod I forgot to apply choke when I first tried to crank it. It started, but ran poorly. Previously, it wouldn't come close to running if the choke was off, and even with the choke on, it needed constant adjusting to keep it running. Now, just a little choke and I can pull away smoothly. I'm anxious to see now if my mileage improves.