Motorcycle Repair: Electrical problem, fuel management system, mileage indicator

Question
My son has a 2010 Yamaha VStar950. And of course his warranty is up so there's no help there. His bike wouldn't start so he jump started it. it would run as long as he throttled it but when he let go of the throttle it died and wouldn't start again. He got it running and rode it for about 10 minutes and the indicator lights and mileage indicator would flicker on & off. It finally died and had to be pushed home. Is this a problem with the altinator or something electrical?

Answer
Rick, the first thing to do is to make sure you have a fully-charged, load-tested battery in the bike. Once you know you have a solid electrical base, then you can assess what might else be happening. You need a voltmeter to monitor the battery voltage at idle and above. If the bike refuses to start/run normally with a fresh battery, then you have electronic issues. I assume the bike has fuel injection so either the control module is acting up/damaged/failed or there are loose wires and/or bad grounds that are interrupting the power paths.

If you have a steady voltage reading at idle that does not rise up with increased engine rpms, then you have a charging system issue with the stator/regulator-rectfier or loose/damaged wiring.

If the voltage goes up to 13.5+ above idle, then the charging system is probably fine and the issues are with the fuel management system. Jump starting bikes with car batteries is generally not a good idea, as batteries in bikes are usually charged about about 1-2 amps.

Lastly, if the bike has been sitting for an extended period of time, the fuel may have separated and is either clogging the injectors or has lost its ability to burn effectively.

Bill Silver