My buddy and I were trying to get his '88 goin today and had some weird problems. He has a fairly new battery so after charging it up for a couple hours we hooked it back up and it didnt turn over completely. So we jumped it and it started right up. Once it ran though, if we gave it gas it'd die unless we kept the jumper cables on it. Also, if we did anything like turn the lights on or hit the brakes, the motor revved up. I dunno if these bikes have a fuse box or if theres a lose wire somewhere. Any ideas?

 

Your battery is pooched. Replace it and these symptoms will go away.

 

ya, sounds like a bad battery. i hope you didn't use more than a 2 amp charger to charge it.

i'd get the battery tested first. autozone/checkers can check out car batteries, they might be able to determine if a motorcycle battery is bad. also places like batteries plus can determine if the battery is bad. that would be my first item to test.

 

+1 on the battery. Unless it was stored carefully and lept on a maintenance charger it is probably pooched. The fact that you had to jumpstart the bike tells me it probably wasn't.

KongBastard

 

I (sorta) had the same problem, for some reason there's a spot in the ignition right before you lock the handlebars that leaves the tail light and license plate light on and I left mine on overnight, jumped it, rode to work, for the first 10-15 minutes my tach jumped all over the place, my blinkers either flashed super fast or really slow, by the time I got to work it was fine, then i did the same thing, leaving the lights on AGAIN, and had to be jumped, got home, turned it off, and when I turned it back on, just barely had dash lights.......installed new pipe, go to turn it on for ****s and giggles and it started right up, no problem at all.......I figure I drained the battery all the way dead (no lights on the dash or anything) and the last ride home finally charged it again so I could start it, now I have to ask...if I had to jump start the bike, the battery was obviously dead, but since it would stay running after I started it, the voltage regulator (rectifier?) was working or it'd die after a few miles....right? Or was the battery just super low and then started charging once I got moving? Not sure I understand the charging systems yet, just trying to get some clarification....

 

it should continue to run with a dead battery IF your voltage regulator and alternator are in good shape. sometimes you have to keep the motor reved, because it doesn't always put out enough volts at idle or lower RPMs.
schroe29, you may want to also look at the electrical connectors going to the voltage regulator. the voltage regulator is underneath the seat, bolted to the bottom of the frame, kinda back between the two coils. there is a ground wire, red connector with 5 wires, and a white connector with three wires. make sure the ground is clean, and the other connectors look in good shape.

 

If the bike won't stay running with out leads on the battery. The battery is toast. Replace the battery and start there. If you have a voltage meter handy then it is simple to see if your alternator is putting out enough to charge the battery. should be 12-16 volts.

The reason for the revving of the motor when you are applying the brakes is because you are drawing off what little charge there is and it is trying to compensate at idle.

 

Lack of proper voltage to the CDI can cause strange things to happen as well!