Topic: Electrical wiring

[rappz7]

So Ive gotten to the electrical on the build and i have a question. The harness is pretty much custom now and far from stock besides the charging system. The power for the headlight, gauges, and dummy lights (built into the new speedometer gauge) are no longer drawing power through the mess of wires that use to be the stock clutch loom but instead drawing power from a single hot wire ran from the regulator/rectifier. My question is this, can I run the power for the dummy lights, and gauge back lights to the same power as the headlight using a single 10amp inline fuse? I did away with the stock fuse box that use to be located in the middle of the handlebars. I figured I can fuse them all with a high enough rated fuse since there no longer individual circuits. Also i should add that the back lights for the gauges as well as the headlight will be wired to a switch that will turn them all on at once when needed. Also can i tap into my backbone wire to hook up my new horn or does it need its own power with a fuse? I have a 1979 cb650. Thanks and as always your input is appreciated.

[calj737]

The problem I see with tapping your headlight power to run the gauges is when you toggle from LO to HI you'll lose your lights, since the tap is made from one of the powered sides. Are you running a key switch? Better to run the headlights and gauges from the switched voltage, not the R/R as its possible the R/R will put out much higher than 12v to the battery based upon need.

Your lights should only "draw" what they need, but I'd still steer clear of what you described. The HORN can grab power from about anywhere that's convenient to you.

[rappz7]

The problem I see with tapping your headlight power to run the gauges is when you toggle from LO to HI you'll lose your lights, since the tap is made from one of the powered sides. Are you running a key switch? Better to run the headlights and gauges from the switched voltage, not the R/R as its possible the R/R will put out much higher than 12v to the battery based upon need.

Your lights should only "draw" what they need, but I'd still steer clear of what you described. The HORN can grab power from about anywhere that's convenient to you.

keyed switch yes. i was going to use a two pole double throw switch with a jumper between the high and low toggle to keep the power consistent to both gauges when switched. I didn't think it be an issue because originally the head light is powered from r/r after its ran through the stock fuse box along with all the other circuits. power from r/r to fuse box to lights switched by the keyed ignition.

[calj737]

That will work. Just might verify the rating of the toggle switch to make sure it can handle the load of the headlight (if you're using a Wattage bulb).

[rappz7]

this is the toggle i was going to use.

[rappz7]

That will work. Just might verify the rating of the toggle switch to make sure it can handle the load of the headlight (if you're using a Wattage bulb).

Its a Heavy Duty 20A 125V toggle. i think that should be more than enough.

[rappz7]

The problem I see with tapping your headlight power to run the gauges is when you toggle from LO to HI you'll lose your lights, since the tap is made from one of the powered sides. Are you running a key switch? Better to run the headlights and gauges from the switched voltage, not the R/R as its possible the R/R will put out much higher than 12v to the battery based upon need.

Your lights should only "draw" what they need, but I'd still steer clear of what you described. The HORN can grab power from about anywhere that's convenient to you.

It doesn't matter that its a much higher rated switch does it? its not like you said going to be too much power for the small bulbs illuminating the gauges will it?

[mystic_1]

i was going to use a two pole double throw switch with a jumper between the high and low toggle to keep the power consistent to both gauges when switched.

I think you'll need some diodes in there, otherwise power will feed over from the LO to the HI circuit and both of your headlight filaments will be lit at the same time.

mystic_1

[rappz7]

i was going to use a two pole double throw switch with a jumper between the high and low toggle to keep the power consistent to both gauges when switched.

I think you'll need some diodes in there, otherwise power will feed over from the LO to the HI circuit and both of your headlight filaments will be lit at the same time.

mystic_1

can i use the diode as the jumper or what? Also is it safe to run a single fuse for all these applications?

[mystic_1]

Well, what you want is a sort of "Y" arrangement with two diodes, so that power from each circuit can go TO the gauges but not back into the other circuit.

HI  ----|>|----\____ To Gauges
LO ----|>|----/

mystic_1

[mystic_1]

Oh, and early CB750's had only one fuse.

Downside:  if that fuse blows for ANY reason, the whole bike dies.

mystic_1

[rappz7]

Well, what you want is a sort of "Y" arrangement with two diodes, so that power from each circuit can go TO the gauges but not back into the other circuit.

HI  ----|>|----\____ To Gauges
LO ----|>|----/

mystic_1

What kind of diodes do i need?