Ok so out of the blue my bike will no longer start. I rode it to class in the morning ( no problems) parked it and was gone for one hour. I come back out and she wouldn't turn over. I turned the key on, dash lights and headlight are on, hit the start switch, get one loud click, bike doesn't turn over, and the lights go out for about 4 seconds. Then they come back on like there was no problem. I hit the switch again and the exact same thing happened. So i push started it, fired up no problem but wouldn't go over 2300rpm. It sounded like it was running on one cylinder. After about 2 minutes of me trying to get it to rev it picked up and continued to run normally. I rode for a good half hour, got home, turned off the key, turned it back on, and tried to start. Same problem as I initially stated. With a little probing battery is reading 12.5 volts normally and when I hit the start switch the voltage(at the battery) wen to .112 volts for a few seconds ( after the loud click ) then it returned to 12.5 volts. I could use your input as to what you think the problem is. I think the starter but i could also use a wiring diagram if anyone has it. 2001 gs500. Thanks in advance.

Sounds like a dead battery.
I assume you have a multimeter, so check the charging system - stator output, and battery volts at 5000rpm.

If your battery volts are LESS than 13ish volts at 5000rpm then its not being charged = Some part of the charging system is at fault.

Battery is crap.

You wanted a wiring diagram - I doubt that this is accurate for your year - only claims to be good for 90-96 - things have changed over time, particularly (some) wire colors and connectors. General idea will be there. If there's a newer one out there, I don't know where, since I have a 90.



Electrical troubleshooting requires a bit of precision to succeed - pardon if this seems pedantic, but I can't see what you actually did, so I have to ask the "dumb" questions...

Starter probably has nothing to do with the problem. I suppose it could be shorted, but that would be exceedingly rare. You have a meter (adiasguy is happy), so check the resistance on it.

If you measured voltage directly from the battery terminals and it dropped to squat, the battery is most likely toast. You can remove the battery and take it to an auto parts or battery store and get it tested (or ride there and have it tested, but right now getting restarted appears to be a problem.)

If you measured voltage from a connector physically attached to the terminal rather than the terminal itself, you might have a case of corrosion where cleaning up the interface to make a good connection will help. Try measuring directly from the terminals first. Then try measuring from the terminal to the connector while pressing the starter (if you get significant voltage, you have found a bad connection, since a good connection will be 0 volts, or at most a few millivolts under load.)

You can also try jumpstarting from a car - if that solves all your problems, the battery is bad. If the jumper cables get hot and the starter doesn't spin, you do have a shorted starter - head out and buy a lottery ticket. Well,  stop pushing the starter button & disconnect the cables before anything melts, then go do that.

The other question is why is the battery bad, and does your charging system work, which can be related, but while a bad charging system will fail to charge your battery, it won't make that battery drop to 0.112V when the starter is pressed.  You can, of course, also try charging the battery, check the electrolyte level if it's not a sealed battery, all that usual stuff. I usually limp them a long ways past where it's more work to keep them going than to replace them - it's not a good system and I don't recommend it to others, but you could have something like a few cells near dry and thus high resistance - the better part of valor is to write the battery off and not get stuck with it crapping out when you need it, but you certainly can refill with distilled water, write yourself a note to remember to check the levels, and recharge, and it might work for a while longer.

Once you have revived or replaced your battery, check the voltage at various RPMs and we will have a better idea of where your charging system is or is not at. If you have a tank bag, you can pop a voltmeter in the map pocket, connect it to the brown and black/white wires in the headlight shell that are not connected to anything on a US bike (sidelight above, colors may or may not be the same for 2001) and go ride. You can also check it standing still.

replace Battery......