by Anton » Sun Dec 21, 2003 4:06 pm
Banshee, if that F650 needs jump-starting after only a few weeks, something's wrong. If it's under warranty, get it taken care of. If not (or if you want to troubleshoot it anyway) do this:
Before riding - before starting the engine - measure the battery voltage. Should be in the 12.6 to 12.8 range, for the old-type batteries and maybe around 13.0 to 13.1 for the gel ones. If it's much below that, the battery is either bad or else it's not getting recharged when the bike's running.
While the bike is running - easiest if you rig a voltmeter to look at while riding - monitor the voltage with the engine well above idle. It should go up to about 14V I think, definitely above 13.7 or so. I'm not sure about the F650 specifically but the Ks and Oilheads are 14. If it's not close, you probably have a charging problem.
Lastly, measure the battery voltage immediately after riding and then after a few days or weeks of non-use (if that ever happens) or at least right before riding again. Some drop is normal, but if it drops more than 0.2V, maybe 0.3V, the battery might be bad.
If, after standing for a long time, the battery voltage is still good and high but won't turn the engine over when thumb the starter, the battery is bad, simple as that.
So to sum it up... there's a good "standing voltage" for the battery, a good charging voltage for the bike, and then an acceptable voltage drop after riding. Find out what differs from that I describe, and you will know the problem.