Rotor question

Sandy803 · Posted: May 13, 2009, 8:21 pm Post subject: Rotor question

Still trying to figure out my charging problem on my 83 hertiage. I'm still have to run a few test, but think I am going to just replace the stator and regulator. Bike charges fine when cold, but once it warms up it stops. My question is about the rotor. If it was bad, had low resistance, wouldn't it stop producing spark and cause the motor to die, or am i mistaking.

Retiredgentleman · Posted: May 13, 2009, 9:14 pm Post subject: Re: Rotor question

Can you give us more details? Have you checked the simple things such as, are the brushes longer than 1/4", 3/8" is better. What is the resistance of the rotor? What battery voltage do you get at idle and at 2500 RPM?

The rotor resistance does not directly determine the spark plug voltage. If the rotor resistance is low, your engine runs on the power from the battery, until eventually the battery discharges and then the spark plug voltage drops off.

gordo · Posted: May 13, 2009, 9:58 pm Post subject: Re: Rotor question

RG is correct,battery voltage is a big culprit on stock ignition compnent's, the trigger on the rotor is just a magnet,low voltage to the pick up will cause missing & no start. Along with weak spark from weak coil to begin with. Just make sure your reading's on the rotor are accurate,& do them with the bike warm if that's when your problem show's up'

xsjohn · Posted: May 13, 2009, 10:08 pm Post subject: Re: Rotor question

Pickup coil creates a voltage......like a guitar pickup............

xsjohn

Sandy803 · Posted: May 14, 2009, 2:01 pm Post subject: Re: Rotor question

Voltage when it is cold is around 13.5 to 14 when running. Battery voltage is good, 12.5 or so just on the battery. Once the bike warms the voltage starts to drop and. Have not done the checks yet. I will be doing them tomorrow since i have the day off. Just trying to get an Idea of what i may be up against

tmol42 · Posted: May 14, 2009, 4:44 pm Post subject: Re: Rotor question

I Had the same issue with my 1980 motor and found it to be the rotor. The continuity in the rotor was fine when it was cold but after it heated up the weak spot in the rotor windings opens up due to expansion. It eventually opened up all the way even when cold. Like gordo suggested, run the bike then measure the rotor and you may find it has opened.

Good luck

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