Helping a NewB with charging system issue....

I have an 81 650 maxim that keeps losing a charge on me ususally when im riding its fine. But if i turn the bike off it doesnt usually have enough power to crank itself over. Seems like it would be the alternator but i checked the battery voltage with the bike off then started the bike revved it to 3000 and the voltage jumped up quite a bit. Could i just be riding the rmp's below a good charging rate or should i just slam a new battery into it.

 

You should have around 12 volts at idle and have around 13 Volts with it revved. First Check your fluid level in your battery. Second if you have the proper voltage is disconnect all of the connections clean them then reconnect and see if that helps. If not I would say that you probably have a dead cell in your.

 

We need more info on your bike; there are a number of possible causes besides the battery itself.

Most common:
-Big connector between the rectifier and the rest of the harness: Unplug it and check all the connectors in BOTH SIDES for any sign of corrosion or being burnt.

-Alternator brushes worn past limit, brush leads corroded, contacts on surface of rotor oxidized and need to be cleaned.

The factory says the alternator brushes need to be replaced at 10,000 miles; mine are at 26,000 and still not worn to the line yet but you do need to check them.

Time to have a peek in the alternator.