Electrical issues - probing

[GSJoe]

As some of you may have read, my bike has contracted an electrical gremlin that is causing to not want to start. I had a little free time this morning, so I decided to grab my multimeter and go probing. First, I checked the battery with the ignition off and got 12.3v and then with the ignition on I got 10.4v. Both of these numbers seem pretty low; what do you think the problem could be? Also, seeing as I may have a bad R/R, is there any way that I can probe it? Third, since I keep blowing bulbs, how can I probe my head light wiring? And last, but not least, is there anywhere else I should be probing?

I apologize for playing "21 questions" but I want to get this thing running at least good enough that I can get it to where I am moving so that I put it into winter storage. Thank y'all for all your help!

[focus frenzy]

12.3 is low and the drop to 10.4 just with the key turned on sounds like you may have a bad battery.
it is posible that the battery may be the cause for the blown bulb, these bikes need a good battery to charge correctly, a short in the battery could cause voltage spikes.

[argonsagas]

Leon has a good point. There will always be a voltage drop when you turn on the ignition, but it shoud not be that much. Why not try a couple of simple things?

For charging system checks, you need a freshly-charged battery.

Disconnect and remove the battery and give it a slow charge, 1 to 2 amps per hour for about 8 hours, or overnight.

Check the voltage, record it, let it sit for a while, then check again. The battery should maintain about 12.6 volts after four hours or more from disconnection.

For the non-start....if the R/R is fried, the bike usually will have no electrical system at all, but if you pull the plug from the R/R, the bike should then have power to the ignition, and it can start.

[pntrdave]

"if r/r is fried your bike will have no electrical system at all."
I stopped at my brother in laws tonight and left the bike Idleing outside well I was in there longer than I thought. Maybe 15 or 20 minutes. When I got on the bike and took off it ran fine for about 5 minutes then I lost a cylinder, then another and another and finally it died altogether. I looked down and I had no power to the electrical system. No turn signals no lights on the instruments no headlight, and no power to the starter button. Called a friend and pretended it was a Harley and put it in the back of a pick up and hauled it home. So about a half an hour after it died I turned the key on and had a real weak headlight and instrument lights, but not enough to even make the starter click. I pulled the battery out and have it on a trickle charger, it was almost completely drained. Any Ideas on the cause of this problem??? GS750T

[GSJoe]

The battery is brand new (1.5mos) but I am going to take back to where I got it and have them look at it. I pulled the plugs off of the R/R while I was probing but it still would not start.

[Anonymous]

charge

Did you say you let it idle for 15-20 mins.? I hope it was real cold out side!!

[scotty]

Re: charge

Did you say you let it idle for 15-20 mins.? I hope it was real cold out side!!

OUCH that idle business was a harley move.
an idle, in my opinion is ok for warm ups but in my book its a never do with these air cooled motors.
Your engine wont stay cool if you try to look cool

[Sandy]

Sounds like a bad cell in your battery that is shorting in between the plates when you apply a load. A 12V battery should put out around 12.6 volts, divide that by 6 cells and you have 2.1 volts per cell. Subtract the dead or shorted cell from the 12.6 volts and voila! 10.5 volts. Take it back.

[GSJoe]

Today, I took my battery back to where I bought it and had it tested. Turns out it was defective, so they replaced it under warranty. After a good charge tonight, I am going to see if it solves the problem.

[GSJoe]

Well I put the new battery in and she started right up. I've got a new problem, now. On my test ride, after I got about to the 100 mi mark, my R/R decided to blow up. After blowing the main fuse a couple times, I decided to unplug it and she fired right up. I had cut my ride short and make the 50mi trip back home in the rain w/ nothing but main power and ignition. Very *interesting* experience for a newbie. At least I made it home safely, though. I had already ordered my Electrex R/R the other day since I thought that was original problem (could've been) so I can't wait for it to get here so I can do some more riding.