Wiring questions

rappz7

rappz7

New Member
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.
 
You can tap into a single power source, but you'll want to make sure your wires are thick enough to handle the current. You also need to balance that with a small enough fuse so that none of the other wires will cook before the fuse does. I use a combination of 18, 16, and 14 gauge wires along with a 15A fuse protect it all.

The output from the R/R should go straight to the battery and then the fused connection from your battery should feed the rest of the bike. This way, if you blow the fuse, the bike loses power and doesn't continue to run from the power output of the R/R.
 
Sonreir said:
You can tap into a single power source, but you'll want to make sure your wires are thick enough to handle the current. You also need to balance that with a small enough fuse so that none of the other wires will cook before the fuse does. I use a combination of 18, 16, and 14 gauge wires along with a 15A fuse protect it all.

The output from the R/R should go straight to the battery and then the fused connection from your battery should feed the rest of the bike. This way, if you blow the fuse, the bike loses power and doesn't continue to run from the power output of the R/R.
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So i have 3 wires that come from the r/r. green, red/white which runs back to the battery ( i assume this is the back and fourth turning ac to dc) and a black wire (which im using to power the bikes lights and gauges. The green im assuming is a ground since its showing multiple points to the frame looking at my wiring diagram. Am i understanding this correctly? Can i use the black wire for power, is it safe and correct? I was going to put an inline fuse on this wire i figure like a 10 amp to protect the lights and gauges. Is this right?
 
Black wire on the R/R is input. The R/R uses it to "sense" the voltage and make adjustments as necessary. It needs to be connected to switched power (any wire that has constant power with the ignition switch turned on).
 
Sonreir said:
Black wire on the R/R is input. The R/R uses it to "sense" the voltage and make adjustments as necessary. It needs to be connected to switched power (any wire that has constant power with the ignition switch turned on).
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ok. so this black wire originally on the diagram is shown going to the following places ignition switch, fuses, and the engine kill and start, im not sure which order though. this is what led me to believe it was a power wire. So what should be powering my headlight and gauges? if that's the case than ive wired some things wrong. Ive never done anything like this but wanted to for the learning experience.
 
The black is power, but it's not power coming from the R/R. It's power going to the R/R (as well as all the other places you mention).

Power coming out of the R/R is the red wire, which goes to the battery positive terminal. The battery positive terminal should then go to the fuse block, and then on to the ignition switch. When in the on position, the ignition switch then feeds power to all of the black wires.
 
Sonreir said:
The black is power, but it's not power coming from the R/R. It's power going to the R/R (as well as all the other places you mention).

Power coming out of the R/R is the red wire, which goes to the battery positive terminal. The battery positive terminal should then go to the fuse block, and then on to the ignition switch. When in the on position, the ignition switch then feeds power to all of the black wires.
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so that means its not wrong. I just misunderstood where the power comes from. So let me see if i have this correct. I have my power from battery (red wire) going to the switched source (ignition) which the black wire is also hooked up to. This in turn when switched on sends power out through the black wire to my lights and anything else as well as the r/r to cycle though again?
 
The hookup sounds correct, but the understanding is still a bit off.

The R/R doesn't cycle power back around. It's a multi-part circuit and that particular portion is something that draws and consumes power.

CB650, right? Don't confuse the two black wires. They're for very different purposes. The black wire that's part of the plug with the white wire is for your alternator and shouldn't be joined in with the rest of the blacks.
 
Sonreir said:
The hookup sounds correct, but the understanding is still a bit off.

The R/R doesn't cycle power back around. It's a multi-part circuit and that particular portion is something that draws and consumes power.

CB650, right? Don't confuse the two black wires. They're for very different purposes. The black wire that's part of the plug with the white wire is for your alternator and shouldn't be joined in with the rest of the blacks.
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Thank you so much for all the information, I appreciate it. I was about to give up on a response and seek council else where but you came through haha. I think i understand it now. And yes 650. i see the black wires your talking about and ill be taking note of it. Thanks for the heads up. Luckily the connectors are all different sizes there so it cant be mixed up.
 
Sonreir said:
Glad to help.

Let us know if you have any other questions.
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I had another question concerning the power wire. Originally the black wire we've been talking about went from the ignition to the fuse block and the r/r from the fuse block it spread off into different wires powering different things like the gauges and dummy lights. I've since removed the stock fuse block as well as many of the other wire since the harness is pretty much custom now and doest have many of the switches and extra bits it use to. Can i run an inline fuse right off of that black wire mentioned earlier to the head light and gauges instead of going through the fuse block like it originally did?
 
Yes, you can.

In the harnesses we make, we generally use a single inline fuse on the red wire leading to the ignition switch. This acts like a main fuse and any short circuit in the harness will blow it.
 
Sonreir said:
Yes, you can.

In the harnesses we make, we generally use a single inline fuse on the red wire leading to the ignition switch. This acts like a main fuse and any short circuit in the harness will blow it.
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Thanks for the response. Ah i didn't think of that. And the single fuse will be good for a headlight, horn, and the back lights on my gauges? i also have separate power for the dummy lights that are built into the speedometer, will the fuse protect those as well? What grade fuse do you usually use for that? What do you think would be best or my situation?
 
The type of fuse you use is determined by the smallest gauge of wire in a circuit.

I use some 18 gauge wire, which has an absolute maximum rating of 16A, so I use the next smallest size fuse: 15A.

However, if you decide to do everything in 14 gauge, that has a maximum rating of 32A, but that doesn't necessarily mean you should use a 30A fuse. Choose the fuse size that will protect your wires and components but doesn't exceed what you expect to be your maximum amp draw across all of your electrics.

For example, at 15V, five Ohm coils will each be using three Amps. Three Ohm coils would each be using five Amps. A 55W headlight will likely pull around 4.5A.

Ohm's Law comes in handy.
 
Sonreir said:
The type of fuse you use is determined by the smallest gauge of wire in a circuit.

I use some 18 gauge wire, which has an absolute maximum rating of 16A, so I use the next smallest size fuse: 15A.

However, if you decide to do everything in 14 gauge, that has a maximum rating of 32A, but that doesn't necessarily mean you should use a 30A fuse. Choose the fuse size that will protect your wires and components but doesn't exceed what you expect to be your maximum amp draw across all of your electrics.

For example, at 15V, five Ohm coils will each be using three Amps. Three Ohm coils would each be using five Amps. A 55W headlight will likely pull around 4.5A.


Ohm's Law comes in handy.
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My main power wire is 14 gauge going to a switch which will control my headlight, high beam, and back lights for my gauges. I believe that the wires for the aftermarket speedo and tach are something like 20 22 gauge not 100% on that. Headlight wires are about 18 gauge. I read somewhere that I need to find the maximum electrical load in watts that it is expected to draw with all the lights etc on at once and than divide by the voltage of your motorbikes electrics (12v) to find the amps. And in turn this determines the fuse needed. Is there anything to this? It also mentions over rating the fuse for the headlight by 50% to account for the initial power surge during warm up. I dont know about all this.
 
All that is more or less correct. I use 15V instead of 12V for the Wattage calculation, though.
 
Sonreir said:
All that is more or less correct. I use 15V instead of 12V for the Wattage calculation, though.
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Alright so i guess my next question would be how i go about finding the wattage for all my lights
 
If you have a multimeter you can measure the amps the bulb pulls when connected to a power source of a known voltage.
 
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