Battery was flat, then 30 mins later okay ...

[StrayAlien]

Hi all,

I had the NC30 out for a track day yesterday. I did seven sessions and it started each time.

After the last session I stopped it, undid the dry break fuel line, and went to start it again (to drain the carbs) and the battery was flat. It basically just turned over a few times then died. Bugger.

But, 30 minutes later after packing stuff up I thought I'd give it another go and it just went like normal and started no problems.

Any thoughts?

[Disclaimer and warning: I am a *complete and utter* dipstick when it comes to electrical things - no light on nobody home].

[magg]

Total loss or normal charging system?

Staring issue most likely caused by poor connection in either the +ve or -ve power path to the starter motor provided the battery is ok.

Start by checking terminals at battery, starter relay, starter motor and chassis ground are tight.

Measure voltage at starter motor when engine is cranking and then at the battery when again cranking the engine, both should be 10-11 volts or greater. If starter motor voltage is lower than the battery voltage by more than 2 volts then wiring or starter relay has high resistance, if battery voltage drops below 10-11 volts then battery is flat or faulty.

If high resistance is the cause then measure the voltage across starter relay terminals when engine is cranking, should be less than 1-2 volts, if not suspect a relay faulty. If relay ok then there is a dud cable between the battery and the starter motor.

If low battery voltage is the cause, charge the battery and then do a load test to determine the battery capacity. If normal charging system is still used then check to make sure voltage across battery terminals at 5000rpm is 13-14 volts. If lower or higher then you have a charging system problem.

Also the problem might be intermittent which will complicate the problem because all the checks above might not find a problem. In which case you will have to wait until the problem reappears.

If any of the above is unclear let me know and I will try clarify.

[StrayAlien]

Thanks magg, much appreciated. I feared I would have to delve into that stuff! Yes, I am a self-confessed electrical ultra-uber-nong. Electricity = "the dark side".

The bike has a normal charging system. When it works, I guess.

I'll figure out how to do that stuff you mentioned above and post back. If I figure it out ... and don't burn myself to a crisp while doing so ....

[Cammo]

This happened to an old vfr roadbike I had, infuriating problem!

[StrayAlien]

hey Cammo ... dare I ask ... did you resolve it?