My 77KZ650C1 recently started blowing the main fuse. One time there was evidence of excessive heat on one end of the fuse, and on the fuse box. So I went through the entire electrical system, cleaning each connector and applying dielectric grease. I wasn't completely satisfied that this would fix the problem. So I decided to replace the fuse box with an automotive blade type fuse block. Not my idea. I read about it here first. I also wanted to do Wiredgeorge's coil power mod. I bought the parts to do the coil power mod a while ago, but I wasn't satisfied with the different fuse size used in the inline fuse holder, so I held off on doing this mod. Doing the fuse block mod would solve this problem, so I decided to do both mods at the same time. First I wanted to see how much improvement each change made so I measured voltages before and after. Initially 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, since this measurement is more consistent. 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. I was really surprised to find that 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. I suspect that the headlight and tailight is brighter too. 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, after performing the coil power mod 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 now 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 starting if the choke was off, and even with the choke on, it needed constant adjusting to keep it running until it warmed up a bit. Now, just a little choke and I can pull away smoothly as soon as I want. I'm anxious to see now if my mileage improves.
Getting better power to the coils really improved the way my 650 ran. If you plan on doing the fuse block mod and the coil power mod, I'd suggest just doing the fuse block mod first and seeing how that improves things. If you're still not happy with the results, go ahead and do the coil power mod. If you're not planning on doing the fuse block mod, then I definately recommend doing the coil power mod.
I think I'll change the wiring around a bit so that I can easily switch between the coil power circuit and the oem wiring. This will allow me to easily compare the two, and easily revert back to the oem wiring if the new coil power circuit ever fails.