Battery problems

[kbuikema]

Hello, Last year I bought a 1971 XS650 1B. Now I am running into the following problem.

With a fully charged battery, I kick-start the engine in one go. After a short ride, the engine won't start anymore. I tested the voltage regulator. The ohmic resistances are fine.

Next, I measured the voltage before starting with a charged battery. It is 12.7V. Immediately after starting, I measure 0V at the terminals. When I turn the engine off, I measure 12.7V again.

What could be the cause? Dynamo, rectifier, or is the battery defective? The current battery is a gel battery.

 

[Its been a long time]

With the engine running, you measure 0v at the battery terminals? The ignition system runs off the battery. You need ~12v on the coil primary winding to get a spark. Something doesn't sound right.

I think firstly I would be looking at the rectifier. Then load testing the battery.

 

[kbuikema]

I measured again just to be sure. When the motor is running, I measure 0V. If I disconnect the positive terminal from the battery, the motor stops. So I cannot measure what voltage is coming from the rectifier.

 

[Its been a long time]

OK. Something isn't right here. The ignition coil cannot generate a spark with 0v. I think I would measure the voltage at the coil primary winding to see what it is while running.

You can test the rectifier diodes easily when not running. There's a full explanation of tests to the charging system in the forum technical section.

While you're testing the rectifier, you can easily test the rest of the charging system too. Take a look at the carbon brushes as well.

While you're doing that, probably best to load test the battery too. 12.7v doesn't mean the battery is good.

 

[kbuikema]

I have tested the diodes of the rectifier. They are good. I am still testing the alternator. If that is good, there is probably a short circuit internally in the battery. Thanks for the help!

 

[Its been a long time]

Thanks for the feedback. Please keep us updated with the solution to the problem.

 

[kbuikema]

The multimeter I used only measures a steady DC voltage. At the XS1, the DC voltage after the diode bridge has a half-sine wave. A Fluke multimeter measures this. Ultimately, the voltage regulator showed 11.5 volts. I turned this up to 13.5 volts.

 

[gggGary]