Should the bike run without battery help once it is started with battery ?

A

asfi99

New Member
I think i have an issue with my Alternator on my 1980 SR250 , recently my bike just gave up on a stop light, i tried to clutch start it by giving it a push but nothing, i took the battery off, charged it and it started working again.

My assumption was that the battery on this bike is only needed to start the bike and once the bike is started it should run on its own even if you remove the battery ?

Is that not true ?

I tried by starting the bike and removing the negative from the bike and it just stopped, so the bike def doesnt run if battery is disconnected.

Do you guys think its an alternator issue, any other way to troubleshoot this issue ?

Thanks
 
The battery is necessary, but not for the reasons you're thinking.

Your bike produces power in phases, it's not steady voltage 100% of the time. When the voltage drops, it may happen to coincide with the time when you coil is charging. This can cause misfires and in multiple instances, the bike will stop running.

Three phase power graph, shown:
Electric-Three-Phase


Ignore the voltage and time quantities, they will be different on your bike. The main thing to understand is that the power coming from the alternator is not constant. The battery fills in for the alternator when your charging reaches a "valley".

Additionally, the battery exists in the system to complete the electrical circuit. With the battery removed, it's like adding a giant switch to the bike and setting it in the 'off' position.

A large enough capacitor can be substituted. In either case, however, a faulty battery or faulty capacitor may cause your bike to not run properly or even at all.
 
Easy to check.

Measure the voltage between the terminals of the battery with everything turned off. Should be about 12.4V or 12.5V on a healthy battery.

Now start the bike and idle it. You should get a little more voltage. Maybe closer to 13V. If the voltage doesn't move, that's a little cause for concern, but don't worry too much yet.

Once the engine is warm, rev the bike up to 4000 RPM and check voltage with the engine at that speed. You should be between 14V and 14.5V. If not, you definitely have a problem.
 
Just to add to Sonreir's good advice, the voltage test won't work if the battery is dead or has an internal short. It will drag the voltage output down.

The test is only correct with a properly charged and operating battery.
 
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