This is long; however, I wanted to provide some detail about how I got my bike from electrical weakling to smooth runner supporting a halogen headlight, Dyna 2k ignition and Dyna 3 ohm coils.
I've been battling the electrics on my '77 CB750K since I got it several years back. I should have known something was up when I realized that the previous owner had installed an on/off switch for the headlight. "Self," I said, "why would he do that?"
To make matters worse, I installed a halogen headlight, 3 ohm Dyna coils and a Dyna 2k ignition. The thing is, it usually ran just below maintaining a charge. Rides of about 100 miles were about max before going back to the charger at home.
Here are the steps I've taken to optimize the electrical system on my CB750:
Voltage MeterEarly on, I installed a
Kuryakyn LED Battery Guage which I mounted unobtrusively just below the instrument light panel. It has been immensely useful, especially because I have needed to head home when voltage began to really drop off.
Interestingly, there is a peak voltage RPM for the bike around 3,700 RPM. Any lower, and the alternator is not producing maximum. Any higher, and the higher RPM's cause the coils to consume more voltage. Sometimes, riding was a fun game of keeping RPM's near 3,700.
Bench TestingI bench tested all the components, following the
Charging System Troubleshooting FAQ in addition to procedures in the shop manuals. The individual components checked out O.K. Even with the add-ons, it seemed I should have more voltage, and at any rate, if I wanted to keep the add-ons, I needed to find more voltage.
Shotgun ReplacementsI replaced the regulator with a solid state one, and I replaced the rectifier just in case. The starter solenoid was fairly corroded, so I replaced that, too. I replaced the battery with a Yusa; however, I don't think any of this maintenance made much of a difference. (I wasn't really hopeful, anyway.) Besides, all had checked out O.K. on the bench. As all of these components looked original (except for the battery), I don't regret replacing them.
Contact CleaningUsing a round file, bottled air, contact cleaner and contact lube, I cleaned all the electrical contacts I could put my hands to. I don't think I did a terribly good job, and it didn't make much difference.
Marker/Signal LED'sNext, I replaced the marker, signal and clock illumination lights with LED's. See my FAQ for
Fitting LED Indicators. I tested it at the time; however, I've lost my numbers. At any rate, this change brought me just a bit more voltage. I didn't replace the brake light. At the time, I couldn't find one that was bright enough.
Wiring Harness RebuildI then rebuilt the wiring harness. Before I started, I created a
Color Wiring Diagram in Vector Format. This made life much easier because I could work from a diagram of any size (I printed it to about 24"x14"). Check out the diagram if you have a '77 or '78 K; I also posted a large jpg format diagram.
Rebuilding the wiring harness took much longer than I planned because I did it in starts and stops and because I was absolutely picky. I soldered every connection except at the components, and I wrapped all solder joints with double-wall heat shrink tubing. I've soldered professionally, so I was picky about the solder joints.
To make things more fun, I didn't use electrical tape or cable wrap for the cables. Instead, I wrapped all bunches of two or more wires with heat shrink tubing. This meant that before each solder, I had to consider/cut/place both tubing for the joint plus tubing for the wires that would be cabled together. Plus, I had to do it without heating any tubing while soldering. The entire harness, end-to-end, is encased in heat shrink, except where wires protrude to the components. Oh, and this meant that everything had to be right the first time.
Some have suggested rebuilding a harness by doing it one wire at a time. I did it by marking all the wires with stick-on numbers, taking copious notes and cutting the old harness out entirely. With a larger diagram, it was easy to put matching numbers on each of the wires on the diagram. I built a new harness on the bench, using the old one to match up the cabling, and then installed it working from the electrics compartment out.
Given the problems with corrosion in the contacts of the standard fusebox, I followed somebody else's advice and replaced the fuses with automotive fuses. A changeover is pie because a standard slide terminal fits an auto fuse well.
When I got the whole thing done, I had gained about 0.5 to 0.7 volts! And man, oh man am I much more confident in the state of my electrical system.
By the way, I've used several butane soldering irons, but this Weller is far better than others I've used:
It's about twice as expensive as the others, but I feel it's worth it. I also use a second Weller with a "heat" tip for shrinking tubing.
LED Brake LightA few weeks back, someone pointed me to the
Luxeon LED. The Luxeon is better than the other LED's I've tried for the brake light; however, I think the original incandescent is a bit brighter. The Luxeon, like other LED's, is directional, so I had to add lights for the license plate. I used directional single LED's for the license light, and if I did it over, I would have used at least 3 or mebbe four bulbs instead of 2. The single LED's are dim.
Note that the LED's are directional and do not make use of the reflector, so there's no prob in running wires/bulbs over it.
The Luxeon isn't as low wattage as normal LED's. It draws 3 watts; however, the gain finally pushed my bike over the charging edge! I could ride and ride without the need to put it back on the charger when I got home.
HondaMan Resistor SetI still needed to do some more work because I wasn't quite there yet. I didn't have insurance voltage (the bike wouldn't push the voltage above 12.75 volts). Ahhhhhh, then came the
Hondaman Resistor Set for 3 Ohm Coils. After installing it I am getting over 13 volts at running speeds, always! It maintains 13 volts unless I spend mebbe 15 minutes in town, or if I run the high beam for more than a few minutes. Thanks HondaMan, that was the last piece of the puzzle.
As shown, the resistor set installs just behind the coils.
Woo Hoo! The Yellow Bomber is ready for long rides.
To Be DoneI've been wondering if a rewind for the stator and possibly for the coil this winter might help. Both check out on the bench, but I've wondered if mebbe the stator is producing less voltage after it heats up. I'll test this next.
Edit: 3 AugustI just caught
this recent thread about HID conversion for the headlight. I had looked into this some time back, but at the time, it didn't seem that the technology had matured enough for me to try it.
Edit: 4 AugustBLAST! I thought I had it licked. But not so. See below.
