Electrical issues: No Power

Joe_Delli

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Hi all,
This is my first post and I’m electronically challenged so go easy on me. I recently bought an 81 xs 400 off of Facebook. Bike ran fine when I bought it. Electrical start, lights, dash lights everything worked. The battery died out the first day and wouldn’t charge so I bought a new one which worked for 15 minutes then blew the main fuse.
I’ve tried 3 batteries so far. One blew a fuse and 2 won’t give the bike any power. What battery should I be using?
 
If you are blowing the main fuse, it sounds like you have a short to ground in some major wire. Is the fuse blowing as soon as you hook the battery up or when you try to switch on some specific item? Before you try again, it might be worth a few minutes to look at the wiring around the solenoid to see if the insulation is intact and not grounding to the frame and also look carefully at the fuse box for loose clips and wires.

The battery you should be using is a 12A-A motorcycle battery like a Yeasa YB12A-A, or Mighty Max YB12A-A. Make absolutely certain that you are connecting the positive battery terminal (+ or red) to the rear wiring lug (if your bike is stock), it is the short wire from the start solenoid. Reversing the connection might just fry your electronic ignition, so make sure you take your time doing this.
 
Got it. Gonna order one off Amazon. I’ll find some time to go poking around this weekend. The fuse would blow when I would flip the key but now when there’s any battery on it it gets no power at all. Never reversed the polarity tho the gold terminal on mine is the positive side.
 
I would also remove the headlight from the bucket and check for any melted or damaged wires. It's where the ignition switch wiring connects to the rest of the bike harness. Then, once you get it running again, you may have a charging system issue so you'll want to check that you're getting 13.8 volts or more at the battery at like 2500 rpm. This was the issue I had with my 78 when I first got it, but luckily a replacement voltage regulator from an old dodge can be sourced as a cheap replacement.
 
Got it. Gonna order one off Amazon. I’ll find some time to go poking around this weekend. The fuse would blow when I would flip the key but now when there’s any battery on it it gets no power at all. Never reversed the polarity tho the gold terminal on mine is the positive side.
If one of the batteries you have is correct, you can recharge it using your car if you don't have a battery charger. Just hook it up with some jumper cables and let the car run/idle for an hour or so. Most modern cars only burn a 1/4 or a 1/3 of a gallon an hour at idle.
 
I would also remove the headlight from the bucket and check for any melted or damaged wires. It's where the ignition switch wiring connects to the rest of the bike harness. Then, once you get it running again, you may have a charging system issue so you'll want to check that you're getting 13.8 volts or more at the battery at like 2500 rpm. This was the issue I had with my 78 when I first got it, but luckily a replacement voltage regulator from an old dodge can be sourced as a cheap replacement.
For sure.
I bought a multimeter with the battery. Went with the Mighty Max YB12A-A. Thanks for the advice on testing. Bought the multimeter didn’t really know much about using it lol. I’ll lyk what I find.
 
UPDATE:
I had some time to go over the bike today. Popped the headlight off and it uncovered an absolute mess of wires. I was able to untangle a bit and found some wires that weren’t connected, and some exposed wires. I insulated a bit and the the bike started and ran without blowing a fuse. I shut it down and shoved the wiring back into the headlight. Went to electric start it again, the bike did nothing, I slapped the headlight, the bike started, ran for a sec then the ignition fuse caught a short and burned out. Can people post/give some advice to clean up my headlight wiring.

TLDR: How can I clean up my headlight wiring so it won’t short out? Can you show me how yours is done?
 

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There is usually no good way to neaten up the wires in the headlight bucket. Most of the harness ends up in there, and you do what you can to make sure it all fits.

But neatness is not your problem, a short in wire insulation or plug that is inside or close to the opening of the bucket is. you need to track that down and fix that first.
 
Oh boy, that is a mess and I see a couple cut wires and even a household electrical wire nut. I would start with taping the ends of any cut wires, though they may need attention and reconnecting later if stuff isn't working. For the wirenut, crimp on some proper male/female blade or barrel connectors, but do get the ones that have the plastic shield covering the connection. It's tedious but take your time and only undo/repair one at a time. Once you think you have it and it's running, don't put it back together, but instead press and wiggle different sections of the harness and make sure it stays running. Also inspect for any chafed wires especially where they come through the rear bucket holes.
 
Hi. I just read that batteries like the MightyMax have to be recharged with no more than 14,4V and at a small Amp rate. The voltage regulator on this Yamaha will allow up to 15V which will gradually kill the battery. I don't have any experience with this type of battery but it is said that we are better with standard 'wet' batteries like the Yuasa YB12A-A.
 
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