The Incredible SHREIKING Whizzer:

Discussion in 'Whizzer Motorized Bicycles' started by Hal the Elder, Dec 10, 2008.

  1. Hal the Elder

    Hal the Elder Member


    During my last few rides on Oscar, I've noticed a "shreiking" sound becoming louder with every ride.

    It only happens under full throttle, and is synchronized with the RPM of the rear wheel, as if the drive belt was slipping on the wheel sheave.

    It's not a continuous shreik, but occurs during a portion of the wheel's rotation, slow at first: (shreik..........shreik), then as the wheel RPM increases with the speed, it becomes : (shreik..shreik..shreik..shreik..shreik) etc.

    But this happens only under full throttle, as though the increased engine torque is adding to the condition that causes the shreik

    When I accellerate slowly, with a light throttle, there is never any shreik anywhere from a stop to 30 MPH. I can be cruising along with a light throttle at any speed, but when I give it full throttle the shreiks start immediately, and they're LOUD, like something coming from a cage at the Zoo!

    I think the shreik may be the noise from the belt slipping on the wheel sheave, but only on a portion of the sheave, because the shreik isn't continuous.


  2. Caterwallering

    Hi Hal, wll, I can tell you that your rear sheave is not centered . This can be adjusted by loosening the 18 screws and rotating the rear tire by hand untill the spring tension of the clutch centers the sheave.

    A belt will always slip on the smallest pulley. Therefore it will slip on the clutch pulley for the rear belt, and on the engine pulley for the front belt.

    After you get the sheave centered nicely, check your tensions.

  3. Hal the Elder

    Hal the Elder Member

    Centered In What Plane?


    Do you mean the sheave is not centered laterally, or longitudinally?

    If I loosen all 18 screws, won't the sheave be pulled to the clutch pulley by the belt tension, becoming uncentered like an eccentric?

    Why wasn't Oscar shreiking before?

  4. Concentricity

    Hi Hal, maybe now that Oscar can breathe better he is shrieking for joy?

    IF you loosen only enuf for the pulley to move under tension, the sheave will become self-aligning. I can tell you, that I have done this myself.

    With intake and exhaust opened, engine trying to break in, and belts begginning to wear in, and streach a little , Why WOULDNT it seem to begin to need some adjusting (refinents of adjustments, mostly) at this time?

  5. Hal the Elder

    Hal the Elder Member

    I Guess You're Right, Mike...

    With Oscar trying to adjust to his new life, full of vibrations, stresses, temperature changes, etc, it probably wasn't TIME for him to start shreiking until now!

  6. KilroyCD

    KilroyCD Active Member

    Hal, my bike has a similar problem, but mine doesn't shriek under power, only when I have the clutch lever pulled and at idle. This doesn't happen all the time, but it happens when the belt has gotten sufficiently hot. In my case, it's pulley misalignment. When I take off the belt guard, I can see that the clutch pulley sticks out farther than the pulley that is attached to the flywheel. I will have to take the clutch arm off and mill it down a bit so the pulleys are on the same plane (a winter project). Although I have the slip-clutch, you may be experiencing the same thing with the auto-clutch.
    However, yours sounds like your belt might be slipping a bit. The first thing I'm going to suggest is to get a good belt on there, instead of the one the bike came with (the belts from the factory are only so-so, and stretch fairly quickly). Find a Gates belt that is the same size (mine takes an AX-27, I'm not sure if your auto-clutch takes the same size), and see if that takes care of your problem. If not, I suggest you have a look at this thread:
  7. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    AX27 is correct for the current automatic clutch. Make sure the noise you are hearing isn't the clutch crying for grease.

    Have fun,
  8. Hal the Elder

    Hal the Elder Member

    Auto Clutch Grease:

    HEY Mr. Q:

    When I had my clutch apart to surface the shoes not long ago, I packed the needle bearings with wheel-bearing grease as you suggested.

    I assume this Gates AX-27 belt is for the clutch/wheel sheave...right?

    The shreik being dependent on throttle setting is what puzzles me...a misalignment would be a problem whether the throttle was light or full, wouldn't it? A slipping belt can be understood, however.


    (This warranty gives you specific legal rights, which may vary from Whizzer to Whizzer)
    Last edited: Dec 10, 2008
  9. KilroyCD

    KilroyCD Active Member

    Hal, if I might be allowed to respond (I know your question was directed to Quenton), the AX-27 belt is the one from the flywheel to the clutch. As to the question of misalignment, mine shrieks when I have the clutch lever pulled in, so the flywheel pulley is rubbing a slack belt on one side. Somehow this noise does not manifest itself when the belt is tight.
    That's why I was thinking your belt might be slipping. Also, I figured you probably have the original belt, which I had found to stretch quickly and extensively on mine. That's why I swapped it out for a Gates.
  10. Hal the Elder

    Hal the Elder Member


    No problem...I welcome all interjections that are pertinent to the discussion!

    The belt from flywheel to clutch can't be the problem in my case, because the shriek only starts when the rear wheel begins to turn under full throttle, and increases in step with the wheel RPM.

    If anything, this should be a sign of rear belt slippage, but I checked the runout on my wheel sheave, and there is no detectable runout that I can determine with a reference marker alongside the sheave.

    Last edited: Dec 10, 2008
  11. KilroyCD

    KilroyCD Active Member

    Hal, that could well be the case. both belts are made by the same maker, and are of only middlin' quality. It would behoove you to replace both belts.
  12. Hal the Elder

    Hal the Elder Member

    Belt Source?

    OK, KILROY...

    ...are these belts that can be found at Pep Boys, or are they Whizzer-Specific at about $600 each?

  13. KilroyCD

    KilroyCD Active Member

  14. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Hal,

    I am having a sale on Whizzer OEM belts. 1/2 price only $150.00 each [LOL].
    Use an AX27 front belt. The AX number isn't the length, but is always 2 numbers different than the actual size. For example the "notched" AX27 [gates part number 90122027] replaces the 4L290, both are 29" belts. Let us know what you find.
    Have fun,
    Last edited: Dec 10, 2008
  15. Hal the Elder

    Hal the Elder Member

    Thanks, Yorlik!

    There's a Gates retailer not far from me, in the next town.

    My rear belt is an AX-62, and it's NOT a Gates!

    Last edited: Dec 10, 2008
  16. WZ507

    WZ507 Member

    AX Belts

    You can sometimes find AX series belts at auto supplies (NAPA), but more often at industrial bearing supply houses. The AX-27 belt is an industrial heavy duty belt where "A" refers to the cross-section (1/2" x 5/16"), X refers to a notched belt rather than a solid belt (A27 would be unnotched), and 27 is the length of the belts inner circle in inches. This differs from automotive belts and L series belts that are more often measured by the length of their outer circle. Strange how the automotive and industrial businesses measure belts differently. See the following link for belt sizes, types, and nomenclature.

    If you don't have local vendor conveniently located you can find any industrial belt at McMaster-Carr. and type "AX v-belts" in the "Find Products" search box

    Regarding your slippage issue, if the sheaves and belt are clean and free of oil, it is most likely the clutch output pulley that is slipping, as you would never slip the belt on the large rear wheel sheave due to the huge amount of wrap it has there. Better tighten that rear belt a bit more and try it again. Also be sure you maintain a nice balance between the front and rear belt tension, as tightening the rear can loosen the front.
    Last edited by a moderator: Dec 15, 2015
  17. Hal the Elder

    Hal the Elder Member

    Tightening the Rear Belt:

    HEY WZ507:

    Do I loosen the rear axle nuts and yank the wheel rearward?

    (This would affect the rear brake adjustment too...)

  18. KilroyCD

    KilroyCD Active Member

    Hal, WZ507 has a point. I'm inclined to think it's the flywheel to clutch belt that's squealing, especially if the sheave is slightly off-center (as it is on mine). The belt is probably causing the clutch to move in unison with the sheave. The only pulley that is not able to move with the undulation of the sheave is the flywheel pulley, and that is probably where the squeal comes from each time the sheave comes to its foremost position during the rotation of the wheel. This causes the clutch to move on its arm and relaxes some of the tension on the belt leading to the flywheel pulley.
  19. Hal the Elder

    Hal the Elder Member

    That's A Plausible Diagnostic Assessment, But...

    ...what do I do now?

    I'm all ears!

  20. KilroyCD

    KilroyCD Active Member

    Make sure your rear belt is as tight as you can make it, and replace the front belt with a Gates AX27. You may have to take the belt off the sheave, then move the axle back very slightly in the dropouts. Tighten everything back up and roll the belt back on.