I'm getting some charging problems, and I'm posting here cos I'm stumped...

• Over time my battery runs flat.
  
  I can bump/jump start it and it will run off its own power, but as soon as the revs drop or I turn the lights on (anything with a high power usage) the bike dies.
  
  I'm not measuring a charging voltage higher than the battery's own voltage (ie the voltage across the battery measures the same whether the bike is running or not)
  
  The resistance across the yellow wires for the alternator is 1.5 ohms.
  
  I can't detect a current leak when the bike is off, and checked the whole electrical system for shorts. Including the red/white wire between reg/rect and starter relay (I read that it can decay)
  
  Recently replaced battery and regulator/rectifier.

So I don't know what's wrong. My guess is that I'm still getting some power from the alternator (the bike runs after being bumped), but not enough to charge the battery.

Any suggestions of more things to test, or what the problem may be?

Do you have a multimeter and a haynes manual? If so test the reg/rec and the alternator . If it still runs with a flat battery it's probably the reg/rec thats fried

dunkenb wrote:Do you have a multimeter and a haynes manual? If so test the reg/rec and the alternator . If it still runs with a flat battery it's probably the reg/rec thats fried

I do and I have. I initially thought it was the reg/rect so I replaced it. Same problems...

If its 1.5 ohms think its supposed to be between 0.1-0.5 , mine gave the same readings as yours and the windings on the back of the alternator coils were fried. Best take it off and have a look.
Could be a break in one of the yellow wires.
New alternators are about £70 from wemoto or about £30 second hand on fleebay.