Let me preface by saying that this fix assumes you have a MOSFET R/R like the Compufire I installed on mine. You may need to modify some steps to keep the stock R/R wiring.
During the restoration of my '93 VN750, I unfortunately did not take the time to clean or modify the wiring harness to increase the reliability. I have been chasing electrical problems for about two months. My only modification as of a couple days ago was to get rid of the stock R/R and go to a MOSFET unit. Not long after I started having issues with the bike dying from losing power feed from the ignition switch, turned out to be full of dirt. My headlight also did not work, or the radiator fan. Next my starter solenoid died, then I lost power to the rear cylinder coil. Truly frustrating. The last straw was when I moved the main harness from under the tank to on top of the rear valve cover to make for a cleaner look, which interfered with removing the battery. So, after much research I decided to modify the entire harness from the petcock area to the back of the bike.
Figure 1
Pin 1: White/Red wire coming from starter solenoid. Main power feed.
Pin 2: White wire fed thru 30 amp fuse. Feeds ignition switch and the fan.
Pin 3A: Lead for 1st accessory.
Pin 3B: Lead for 2nd accessory.
Pin 4: Black/Yellow wire to fan switch, grounds the fan relay.
Pin 5: Blue wire, switched side of the fan relay, powers the fan.
Pin 6: Brown/white wire fed from the ignition switch. Has power in the "ON" position.
Pin 7: Normally left blank, used in bypassing the headlight relay. This is where the blue wire is moved to. Fed through 10 amp fuse.
Pin 8: Blue wire, switched side of the headlight relay, sends power to the reserve lighting unit.
Pin 9: Yellow wire from the stator, feeds power through a diode (since it's alternating current) to turn on the headlight relay. Once turned on the relay becomes self powered through another diode.
Figure 2
Pin 11: Black/red wire (may vary on some years), feeds power to the starter safety relay from the starter button.
Pin 12: Black wire (shows Y/G in the manual), grounds the relay if in neutral and/or the clutch is in.
Pin 13: Yellow/red wire, switched side of starter safety relay. Feeds power to the starter solenoid.
Pin 14: Black/white wire from the ignition module. Will kill ignition if not grounded.
Pin 15: Light green wire, to the neutral switch.
Pin 16: Green/white wire, to the kick-stand switch.
Pin 17: Red/blue wire, fed power through 10 amp fuse for the tail lights.
Upon inspection, it is evident that the headlight and starter safety relay circuits can be eliminated. Anyone who has owned a bike more than a month knows not to ride it with the kick stand down or start it in gear. Also, for anyone who has installed a R/R with leads that go straight to the battery, the stock R/R wiring can be gotten rid of.
*IMPORTANT*
Re-read that underlined sentence. Be aware of the dangers of accidentally taking off with kickstand down or starting the bike in gear!
Now that that's out of the way, we can determine how to get rid of the junction box entirely. The junction box is a never ending source of problems for Vulcan owners. I ordered replacement relays to fix mine, only to find that the inside was corroded. Good job Kawasaki engineers on the (lack of) weather sealing.
Another reason to do this is that by now your connectors are getting old and cracked, and tend to not survive being removed many times (as many Vulcan 750 owners have to do) to help diagnose electrical problems. Mine were pretty toast.
During the restoration of my '93 VN750, I unfortunately did not take the time to clean or modify the wiring harness to increase the reliability. I have been chasing electrical problems for about two months. My only modification as of a couple days ago was to get rid of the stock R/R and go to a MOSFET unit. Not long after I started having issues with the bike dying from losing power feed from the ignition switch, turned out to be full of dirt. My headlight also did not work, or the radiator fan. Next my starter solenoid died, then I lost power to the rear cylinder coil. Truly frustrating. The last straw was when I moved the main harness from under the tank to on top of the rear valve cover to make for a cleaner look, which interfered with removing the battery. So, after much research I decided to modify the entire harness from the petcock area to the back of the bike.
Figure 1
Pin 1: White/Red wire coming from starter solenoid. Main power feed.
Pin 2: White wire fed thru 30 amp fuse. Feeds ignition switch and the fan.
Pin 3A: Lead for 1st accessory.
Pin 3B: Lead for 2nd accessory.
Pin 4: Black/Yellow wire to fan switch, grounds the fan relay.
Pin 5: Blue wire, switched side of the fan relay, powers the fan.
Pin 6: Brown/white wire fed from the ignition switch. Has power in the "ON" position.
Pin 7: Normally left blank, used in bypassing the headlight relay. This is where the blue wire is moved to. Fed through 10 amp fuse.
Pin 8: Blue wire, switched side of the headlight relay, sends power to the reserve lighting unit.
Pin 9: Yellow wire from the stator, feeds power through a diode (since it's alternating current) to turn on the headlight relay. Once turned on the relay becomes self powered through another diode.
Figure 2
Pin 11: Black/red wire (may vary on some years), feeds power to the starter safety relay from the starter button.
Pin 12: Black wire (shows Y/G in the manual), grounds the relay if in neutral and/or the clutch is in.
Pin 13: Yellow/red wire, switched side of starter safety relay. Feeds power to the starter solenoid.
Pin 14: Black/white wire from the ignition module. Will kill ignition if not grounded.
Pin 15: Light green wire, to the neutral switch.
Pin 16: Green/white wire, to the kick-stand switch.
Pin 17: Red/blue wire, fed power through 10 amp fuse for the tail lights.
Upon inspection, it is evident that the headlight and starter safety relay circuits can be eliminated. Anyone who has owned a bike more than a month knows not to ride it with the kick stand down or start it in gear. Also, for anyone who has installed a R/R with leads that go straight to the battery, the stock R/R wiring can be gotten rid of.
*IMPORTANT*
Re-read that underlined sentence. Be aware of the dangers of accidentally taking off with kickstand down or starting the bike in gear!
Now that that's out of the way, we can determine how to get rid of the junction box entirely. The junction box is a never ending source of problems for Vulcan owners. I ordered replacement relays to fix mine, only to find that the inside was corroded. Good job Kawasaki engineers on the (lack of) weather sealing.
Another reason to do this is that by now your connectors are getting old and cracked, and tend to not survive being removed many times (as many Vulcan 750 owners have to do) to help diagnose electrical problems. Mine were pretty toast.