Looking for suggestions of where to start investigating my latest problem. I have limited skills, but with my multimeter I have determined that my battery is not being charged when bike is running (12.8v when off, 12.4 when running at 2000rpm and I understand it should be reading 13.5v minimum). Battery is less than 12mth old, has been professionally tested to be ok. Bike was unable to crank after about a 30min ride. (This happened also with previous battery, but that one tested as failing under load, hence the new one).
Before I harrass my very good mechanic mate, I want to try and diagnose it myself….what should be my first plan of attack?
The most likely and most common charging fault is the generator rotor going bad, you should have 14 plus volts with the lights on at 3000 rpm, you can test the resistance of the rotor with a meter across the 2 brass slip rings, any less than 4.3 ohms and the rotor is bad
I had one fail last year, was charging ok and measured 4.4 ohms cold,so i went out on the bike and it died after 20 miles, when i got home in a van i removed it and put it in the oven at 100 deg centigrade then measured and was 0.0 ohms
They can also cause intermittent charging problems when starting to go bad
So i had it rewound and is fine now