checking alternator output

[richrd]

The bike will run on battery without alternator input...for a while. At some point, you will need to recharge the battery. I like to think that the bike's ignition system pulls energy from the battery while the alternator's job is to refill the battery.
Kurt in S.A.

the problem is you seem to think i know nothing about mechanics because I asked (a very specific) question.

I did not say "what's wrong with my bike" I asked if there was a way to check alternator output. I am well aware of how far a bike will run on a total loss system. I am well aware of how to measure battery voltage and what should happen when I rev the motor.

I have built, rebuilt, restored, or repaired more British bikes than I can count, but this is the first Beemer I've worked on.

But hey, if you ever need advice on a Norton let me know. I'll tell you which way to turn the throttle.

[schrader7032]

Sorry, I didn't mean to suggest anything about your abilities...I really don't know much about your situation. Guess we do now! I'd have something to ask about re: Nortons if I had purchased that Commando back in the mid 1970s...unfortunately, it didn't happen.

Seems like you had some input by others about how to get some feedback on the alternator performance. Has any of that helped?

[srankin]

I am not doubting your abilities but you do know that the point for checking charging system health is at the battery?

Again, with the stock system, at idle, the light will come on, that is normal. At 2000 rpm and above, the red light should be OUT. Fudge a little and maybe 1800 rpm. If you are riding normally the light should be OUT. If it is on while riding and not at idle, there is a problem. If you are getting 13.5 to 14.5 volts at the battery at 2000 rpm and above and you are having problems starting, then the battery is on its way out. If you are not having any issues with starting and the light goes out while riding, you have no problem, that is just normal for an airhead.

Normal resting battery voltage: 11 to 12 volts.
Normal charging system voltage at 2000 rpm or above also measured at the batteryL 13.5 to 14.5 volts.

Voltage with regulator blue and black wires bridged, taking out the Voltage regulator in the system, voltage should be 15 to 18 volts again measured at 2000 rpm or above and at the battery.

Yeah, it is not a Norton, it has its own quirks. St.