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Rewiring a whole motorcycle ignition switch wire gauge capacity limit


juliushonrada's Avatar
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08-14-17, 01:02 AM   #1  
Rewiring a whole motorcycle ignition switch wire gauge capacity limit

I am having a problem with my motorcycle lights getting weak and sometimes totally turning off when using the horn , i would like to rewire it with a single 16 gauge wire that will feed all the positive for the headlights , horn and the signal lights and tail light the problem i am facing while trying to put it all up together in my brain is that the ignition key switch wires are like only 20 gauge and is small and that is also true for the other control switches , they just become the weakest link in my circuit.

The solutions i have in mind:
1. Use a 30amp bosch relay that is controlled by the ignition switch but have a high current wires direct to the battery that will supply positive current to all of my electricals, this beats the purpose of me rewiring the bike because i can just do this without removing anything but i want to ditch my old harness and make a cleaner looking bike with few less wires this will actually add more wires.

2. Ditch my old harness use a 16 gauge wire coming straight to the battery , resolder a 16 gauge wire to the ignition key switch , and to the light/horns switches, this way i wont need to use a relay right? but its a hell lot of work...

Can anybody shed light , how about run a 16 gauge wire to the battery going to the ignition key switch then out of that i will just add a 16 gauge wire again?
Will it burn the smaller ignition key switch wire(around 20 gauge)? or it is fine? im not sure about this but i believe length is also a factor in the current carrying capacity of the wire and the ignition key switch wires are very short can anyone confirm this?
Thanks in advance

 
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08-14-17, 04:11 AM   #2  
You don’t state if this is a new or existing problem. Unless someone has added electrical accessories not standard to this vehicle, I would think the manufacturer sized the wires, alternator and battery for the loads. Before proceeding, I would get the battery and alternator tested. In the meantime, determine the amps for each electrical load and determine the gauge wire necessary for the amps. If it wasn’t a battery or alternator problem, it is the positive wire from the battery to the switch, negative wire from the battery to chassis or the positive wire from the switch to the positive junction for the loads. I would replace the wires with a gauge larger than that defined by the load determined above. Once you have the issue corrected, then you can proceed to cleaning up the wiring. Good luck.

 
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08-14-17, 06:08 AM   #3  
You could have a loose or corroded connection somewhere in that circuit.

At twelve volts, the added resistance from a loose connection could make the difference between correct operation and lights dimming severely.

Loose connections can also exist where wires are attached to different parts of the frame for the negative connection and thee is corrosion where the respective frame parts are connected to one another. This latter problem can be fixed by adding wires to complete the problematical parts of the circuit so as to no longer rely on the frame.

Substituting a fatter wire for part of the run of a thinner wire will not endanger the remaining part of the thinner wire, provided that fuses were properly sized for the circuit.

 
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08-14-17, 06:17 AM   #4  
A short length of thin wire still in the circuit will not nullify the benefits of substituting fatter wire in most of the circuit for the purposes of combatting voltage drop, even if the thin wire was closest to the power source.

 
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08-14-17, 07:02 PM   #5  
First, welcome to the forums. Could you please advise the make and model of your bike. It would also be good to know if you or a previous owner added anything to the electrical system.

Have you investigated the output of the generator and the condition of the battery. Most bikes have marginal excess capacity and overloads can destroy very expensive components. I would not recommend any changes until you check out the existing components as related to the rated output of your charging system.


Woody


You can trust your car - and a whole lot more - to the man who wears a star.

 
juliushonrada's Avatar
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08-14-17, 10:44 PM   #6  
The bike is a 1998 2 stroke Yamaha RX135 it uses a light/chargecoil with halfwave rectification 3 wires total 1 for light 1 for charging 1 ground, i already converted the coil and removed its ground and use a fullwave rectifier using the 2 remaining wires as the AC sources. on idle without a battery it produces 3 volts and when revved at around 10k rpm it produces 16 volts, with a battery it produces just around 12-13.6 volts never went any higher.

I also converted the headlights and the tail light to be switched on and be operated by the battery instead of the light coil it is tapped in the ignition key switch positive output wire.

On my stock harness the recommended fuse was 10AMPS in the user manual, this can only mean that the bike circuit is just designed to operate below 10 amps and the wires are very thin for my setup

 
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08-15-17, 02:41 AM   #7  
Theres no edit button, i forgot to add that 90% of my harness is useless because my lights/control switches/etc almost everything is not stock anymore because my bike is very old and is almost obsolete everything had been replaced except the cdi and the ignition/pulser/primary coil

 
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08-15-17, 04:48 AM   #8  
Unfortunately you have created a one-of-a-kind electrical system on your bike. Only you know how and what components are connected. Therefore other peoples comments are interesting at best. By the way, what are you using for voltage regulation and how is it connected?

 
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08-15-17, 04:56 AM   #9  
Unfortunately you have created a one-of-a-kind electrical system on your bike. Only you know what and how components are connected. Therefore other people’s comments are interesting at best. By the way, how are you regulating voltage in the system?

 
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08-15-17, 05:37 AM   #10  
Yeah , the headlights , tail light and the horn is connected to ignition key positive output wire , and the negative all just goes to the ground chassis.

The whole system is protected by the regultor/rectifier its a generic GY6 5 pin rectifier with 2 AC sources

 
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08-16-17, 04:40 AM   #11  
As I stated in an earlier post, your bike's electrical system is unique and only you can troubleshoot it with any certainty unless you can provide a wiring diagram with every component identified by a part number and wires identified by gauge. I looked up the rectifier number you provided and came across an article (web site below) that shows how easy it is to get into trouble when substituting electrical components without verifying form, fit and function. Good luck.

4 pin to 5 pin regulator swap - help needed | SCOOTER PROFESSOR

 
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