Question-------------------------
Followup To
Question -
My bike will start when the battery is jumped with a fresh battery. However, as soon as i remove the jumper cable , the bike stalls. It appears to me that there must be an alternator problem or something with the electrical system that does not allow the battery to charge up and keep the bike running. it is obvious that i don't know that much about the electrical system, so, i would like your opinoin. I am not sure what is required to keep it running unless it has an electrical fuel pump.
Am i even close by suggesting the alternator?
Thanks for your assistance.
Harry
Answer -
Harry... Does the battery in the bike have a full charge?
If you are jump starting a dead battery with a live one and then expecting the bike to run... it won't.
The ignition system is battery-powered, like a car (an older car, I guess), using points and a condenser. The "alternator" of the bike is only capable of keeping a fully-charged battery in a fully-charged state. It will NOT charge up a dead battery and keep the engine running at the same time.
1975-later models have always ON headlights which draw even more power from the electrical system. Buy and install a new, fully-charged battery and it should be fine to run again, if everything else is fully functioning (fuel system, etc.) Make sure that the brake light is not staying on from a misadjusted or broken brake light switch.
This will run the electrical system down again. It is a very delicately balanced system.
Bill Silver
Bill,
Thank you for the timely response. I charged the battery up all the way. It is a new battery (June '05), so didn't need much charging. When i started the bike up, i had a voltmeter on the battery terminals. With the bike running i noticed the voltage starting to drop off. As it got less and less, i turned the bike off as not to drain the battery down again.
I may add that i just bought this bike from someone and don't know the history of it. I looked over the wiring and from what i can see, there are no shorts. The battery is OK when just sitting there. I did replace the brake light as it was not working and i will check if it is on at all times as you suggested.
Thanks again.
Harry
AnswerHarry, the charging system doesn't really even out until the engine is running around 3,000 rpm. With the headlight always on the deficit adds up in a hurry. If you are not seeing any increase in voltage output above 3k, then probably the rectifier has failed or the wiring connections to it.
Rectifiers can be checked with an ohm meter by switching the leads back and forth on the wire pairs. Measuring through the diodes, you will get a low resistance reading in one direction and a high reading when you swap the leads of the meter on that wire pair. Red is + output to the battery and Green is generally ground. The other leads... usually brown, yellow and/or pink are the leads from the stator, which is feeding AC volts to the rectifier, that then turns the AC to DC volts for the battery.
www.electrexusa.com for charging system troubleshooting.
Bill Silver
