Topic: 75 CB550K Electrical / Lighting problems

[Porscheguy912]

Hello all,
I have a 1975 CB550K. I just changed out the handle bars to some low drag bars. I never thought i would have such a problem with the wiring because its all color coded. I just replaced the rectifier before i did the bars to get it generating again. Here is the problem....
The turn signals dont flash and when they come on, the buzzer buzzes for a second or two and the respective light comes on, but its slow to come on and it starts out dim and then gets brighter and stays illuminated. The rear turnsigal does not light. I have replaced the flasher unit and sitll nothing. I did notice that the flasher i pulled out only has two leads and there is a third green wire hanging there not connected.

I just replaced all four turn signals with new ones. Although, on the front ones, I got single filament instead of dual. (So no running lights) I just crimped a female wire terminal on the leads for the running lights and taped them up. The rear turn signals havent worked since i put them on. (as far as i can tell the actual lights are grounded just fine as they are bolted right to the frame)

I rode the bike for a week or so with no tunsignals, then one day my tail light stopped working, and a few hours later the brake light stopped working. ( I checked for power at the brake light foot pedal switch and there is power there, but i have'nt ventured further than there.

Also, my headlight is stuck on "Bright" and will not switch to "low". I know the wires in the switch are bad and they are shorting together. I will try to fix that soon.

A few weeks ago i had a unrealated throttle/ crarb problem. I either didnt tighten or didnt tighten enough the nuts tha adjust the carbs thottle position and the bike was idleing at like 5,000 rpms. I was thinking that maybe at that rpm the grenerator melted some wires in the bundle of wires behind the rectifier, (the rectifier was quite warm) and thats why my tail light an brake light dont work.

Any thoughts on this before i just run new wires for things?

[TwoTired]

Do you have a multimeter and a wire diagram for your bike?  Almost a requirement for isolating electrical issues.  And, certainly data from measurements will help in an on line dialog.

The stock flasher unit is sensitive to the bulb resistance and is tuned for the ones installed stock.  What wattage bulbs did you install at the flasher positions?

The green wire near the flasher unit is a ground that three prong flashers need to operate correctly.  with your modification, you may need a flasher unit that is three prong and not load of voltage level sensitive.

Also, never assume the frame ground is a proper return path to the battery,  Honda relied on the solid green wires to provide that function.  All lighting should have a power delivery wire and a return green wire connection.

The wires behind the rectifier include a green wire that is bundled, and terminates to frame ground up near the coils. The entire length of wire in that bundle can overheat and melt, not only its own insulation, but that of other wires in the bundle, too.  Many odd electrical things can occur when wires in that bundle cross connect.  I had a 76CB550F that this happened to. I unwrapped the bundle and replaced each of the damaged wires.

I was thinking that maybe at that rpm the grenerator melted some wires in the bundle of wires behind the rectifier, (the rectifier was quite warm) and thats why my tail light an brake light dont work.

While the alternator has the power to melt wire insulation, it will only do so when other faults are present. 

Any thoughts on this before i just run new wires for things?

Adding more wires won't correct the faults unless you bypass each and every fault in the existing wiring.  Are you prepared to make a new wire harness?

Cheers,