Altenator rotor noise

Discussion in 'Electrical' started by Teague, Mar 28, 2010.

  1. Teague

    Teague New Member

    I've got a late model Evo and it appears that the rotor has gotten a little slop in it where it rides on the output shaft. I get a slight tap at low rpm or when turned over by hand. Replacing the rotor is not an option at this time. I am considering tacking the rotor to the compensator hub in a couple of places. Does anyone see any ramifications to this quick fix that I am overlooking?
  2. Jack Klarich

    Jack Klarich Guest

    Check the end play on the crank shaft as long as you are in there. I have seen too much end play destroy a few alternators, Jack
  3. shovelrider

    shovelrider Member

    If it is knocking at low rpm I would check the compensator spring pack to make sure it is not the problem.
  4. Teague

    Teague New Member

    End play and Compensator spring pack seem ok as do the ramps on the Compensator itself. It looks like there is some play in the rotor itself. If I turn the engine over by hand the magnets in the rotor will pull themselves forward as it gets closer to the next coil on the stator. You can actually see a shift in the rotor as it advances itself approximately 1/16 of an inch at the circumference.
  5. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    As you can see here:

    ALTERNATOR & REGULATOR - 1999 Harley Davidson FLHR


    There are "teeth" in the rotor hole that mate with the profile on the output shaft. These are a very close (but NOT interference) fit. If you have that much movement, it suggests that these "teeth" in the rotor hole are very worn or even sheared off. Two problems:
    1. Rotor can move enough for the magnets to contact the stator coils
    2. "Teeth" have to be somewhere
    I would pull the compensator/chain/clutch basket and see what the problem is. If the rotor is chewed up (hole), you gotta replace it before more serious damage is done.

  6. Teague

    Teague New Member

    I've found the problem, it appears the engine was assembled minus the rotor hub spacer. Thanks for all the replies.
  7. Jack Klarich

    Jack Klarich Guest

    Oops,seen this too on a Sturgis Model it destroyed the Alt and the belt

    NEWHD74FAN Experienced Member Retired Moderators

    Is it just me or shouldn't the magnets be "bonded" and not able to "pull foward", I would be worried that scuffing damage would occur...:newsmile040:
  9. Jack Klarich

    Jack Klarich Guest

    Yeah, they should be bonded and not moving. Is this a stock H D set up or after market like Accel.NewHDFAN IS thiking ahead for you here
  10. Hoople

    Hoople Account Removed

    The planets must be in alignment for you. You somehow escaped $$ damage. Go buy some Chrome with the money you saved. Glad all is well:p