How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Louie Your Own Question
Louie, Technician
Category: Motorcycle
Satisfied Customers: 12462
Experience:  25+ yrs. experience
Type Your Motorcycle Question Here...
Louie is online now
A new question is answered every 9 seconds

I have recently changed my R/R and battery but still having

Customer Question

Hi Jeff. I have recently changed my R/R and battery but still having charging issues. When checking in my garage the stator gives 36 V across each winding at 4000rpm and I see 14+ volts at the battery yet after 100 miles of riding and a few starts the battery will be down to 11.5 volts. I have checked every connection I can see including the starter solenoid and all are remarkably free of corrosion so I am running out of ideas.
Submitted: 1 year ago.
Category: Motorcycle
Expert:  Louie replied 1 year ago.

Hi and welcome to JustAnswer,

Thank you for the question and your patience. With the indulgence of Jeff and should you still need assistance for information purposes only...

Initially, proposed preliminary tries (if have not been done):

  • • re-test the charging voltage as it should be nearer +15V;
  • • re-test the stator;
  • - wire-to-wire resistance something like 0.1~1.0Ω but no resistance to engine ground;
  • - output AC voltage wire-to-wire @ 5,000RPM ~50VAC;
  • • consider having the battery externally charged and then LOAD TESTed (even if new and just for the purpose of eliminating it as a suspect).


Customer: replied 1 year ago.
Hi Louie, thanks for your answer.
Due to my working hours today is the first opportunity I've had to test (make noise) at a sociable hour!
I found the resistance to be 0.9Ω across each winding and 0.5 to ground. The AC voltage wire-to-wire @ 5,000RPM is 68V.
The battery is brand new and I also tried two out of other bikes and they all performed the same after being charged.
I did notice that with lights off the voltage from the regulator does peak at 14.8 volts around 2000rpm but by 5000rpm has dropped to 13V. With the lights on the voltage just continually creeps down, giving me about two hours running before it is too low to restart the engine.
I had replaced the stater a few months ago after the original showed a hot spot on the winding. When the latest charging problem occurred I checked the AC out put and resistance and it was no different from when I fitted the part so I fitted a new mosfet regulator thinking that was the problem. The battery was quite old so I replaced that too but none of this made any difference. Goes this give you any more clues as to what my problem may be?
Expert:  Louie replied 1 year ago.

Appreciate the post back Graham.

Everything seems as expected then except for the "...0.5 to ground..." To my understanding, since this is a 3-phase alternator, none of the winding should show a resistance to engine ground.

Was this resistance measurement done with the 3-wires from the stator temporarily disconnected from the R/R?

Customer: replied 1 year ago.
Hi Louie. Resistance was measured with the R/R disconnected. Resistance is 0.5 ohms between any of the 3 wires and ground. I changed the alternator last year and installed a heavy duty replacement so was reluctant to think this unit might be the problem but it looks increasingly like it has failed again. I will take the cover off this weekend so I can inspect the alternator more closely. Graham.
Expert:  Louie replied 1 year ago.

Thanks for the post back Graham and yes please; would look forward to an update after this weekend or when able.