Wiring setup question

I'm in the process of brainstorming a wiring setup.

I'm setting up my own fuse box to replace the old, busted, gremlin causing factory one, and a thought came into my head. My question is essentially would it hurt anything to leave two of the three key on wires disconnected? My thought is that if I can have the 30a main fuse in it's own holder, then I could wire one of the other ones to trigger a relay drawing straight from the battery to power a fuse block. If those three wires are just power off key then it should work fine, and as an added benefit that isolates the other circuits from the main one, and makes any add on power draws (lights, GPS, radio, phone charger, that kind of stuff) isolated from the factory wiring and switched with the key.

 

the way it works is this on 3 wire systems
main fuse is always hot it feeds the ignition key which directly feeds the tail light and plate light.
the other wire feeds the fuse box head light fuse , signals fuse , and ignition fuse it is a very simple set up.
the main fuse feeds all other fuses and protects the circuits attached to them as well as the tail lights
so 30 amps would be to high 20 amp is standard.
if you do it your way with relays main fuse would not have to be 20 amps (tail lights only)
you would need a 20 amp to 30 amp relay to power your fuse box depending on how much power you want to supply to fuse block.

what I see as the problem is now you have to deal with a relay hope it does not disconnect when you hit a bump, just another component to fail.
you can add more fuses with a longer block. the current fuse block recomended is the type where each fuse has an input not a buss style fuse block where all fuses are fed buy 1 input wire ( funny because that is really how the stock fuse block works after the main fuse.

no gain in what you want to do. you can add more fuses and feed from battery if you need more circuits. Good idea but...

use the KISS method Keep It Simple Stupid ( I am not calling you stupid)

 

I think a previous owner of my bike was in there doing some backyard mechanic wiring. My main thought with what I have in my head is that I am trying to minimize the current flowing through the original wires as much as possible. Also, I have a very nice single input fuse block lying around.

 

on my 550s the main fuse is fed from a heavy guage wire connected to solenoid.
more than enough wire to carry the current flow. for existing fuse block.
I like your idea but I would keep your ignition fuse with the key would hate to have the relay fail and be stranded.
the wire returning to fuse block from key splits off into 3 leads for the fuses. you could use one of those leads to power relay for remaining fuses and other fuses you wish to add.
if you think about it your Idea ends up doing the same thing as Yamaha does just adds a relay and more wires, of course you could also use a multi contact relay.
in this link there is a wiring table for size and current contact relay.

XJ PARTS CATALOG, SECTION D: ELECTRICAL SYSTEM

from that link
If the wire OD is 2.03mm - 2.19mm (.0799 to .0862"), then it's 20-gauge (20g) AWG or 0.40mm squared (metric size).
NOTE: 20g wire is rated for a maximum load of 11 amps of current at 12VDC.

If the wire OD is 2.26mm - 2.42mm (.0890 to .0953"), then it's 18-gauge (18g) AWG or 0.75mm squared (metric size).
NOTE: 18g wire is rated for a maximum load of 16 amps of current at 12VDC.

If the wire OD is 2.48mm - 2.64mm (.0976 to .1039"), then it's 16-gauge (16g) AWG or 1.25mm squared (metric size).
NOTE: 16g wire is rated for a maximum load of 22 amps of current at 12VDC.

If the wire OD is 2.89mm - 3.05mm (.1138 to .1201"), then it's 14-gauge (14g) AWG or 2.00mm squared (metric size).
NOTE: 14g wire is rated for a maximum load of 32 amps of current at 12VDC.
NOTE: 14g wire is the largest size wire normally found in the wiring harnesses on these bikes. Battery cables and the solenoid-to-starter motor cable are larger, of course, but of all the main harness and accessory wiring, 14-gauge is the largest that you'll find.

If the wire OD is 3.49mm - 3.65mm (.1374 to .1437"), then it's 12-gauge (12g) AWG or 3.00mm squared (metric size).
NOTE: 12g wire is rated for a maximum load of 41 amps of current at 12VDC.

If the wire OD is 4.32mm - 4.48mm (.1701 to .1764"), then it's 10-gauge (10g) AWG or 5.00mm squared (metric size).
NOTE: 10g wire is rated for a maximum load of 55 amps of current at 12VDC.

 

Already done. As 550 stated...the stock configuration is engineered to flow the current in one direction (diodes) and use the least amount of current necessary to sustain adequate power to each component throughout the ride range (regulator/rectifier ).

Gary H.

 

Please keep in mind that the XJ series of motorcycles were developed specifically to match-or-exceed the best motorcyles that Honda was building at the time. Yamaha was out to take as much as Honda's market share as possible, so they engineered the heck out of the XJ series. Can the wiring be improved upon? Of course, but that is going to require building a harness from scratch. Put a multi-input ATC fuse block in and go ride. Save the rest of your upgrade plans for the winter.

 

Exactly.

Gary H.

 

My 1983 XJ750 Seca..I replaced my fuse box with 6 way glass tube type. Wanted to keep it close to original. Stainless steel and brass, should last for years to come. Perfect fit under the seat. No mods to seat just enough room.
I have since started using #5 fuse for a alarm system, works great.

 

I think if you draw your idea out on paper you will see how much extra wire you will need.
The only way to gain anything is use bigger wire to reduce voltage drop in the harness

 

Why???? Unless P.O. totally butchered harness follow wiring diagram and set up fuse block same way. Will save you lots of trouble , you do not want to be on the side of the road after dark with blowing fuses trying to figure out a wiring problem. Or to smoke a TCI, or starter OR?? if you wire it wrong. Cannot agree with K-Moe and rocs 82650 enough the engineers knew what they were doing when they built these bikes.