The Incredible SHREIKING Whizzer:

[Hal the Elder]

Hello...

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.

HAL

 

[MotorbikeMike]

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.

Mike

 

[Hal the Elder]

Centered In What Plane?

HEY MIKE:

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?

Thanks...
HAL

 

[MotorbikeMike]

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?

Mike

 

[Hal the Elder]

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!

HAL

 

[KilroyCD]

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: http://www.motoredbikes.com/showthread.php?t=14390

 

[Quenton Guenther]

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

Have fun,

 

[Hal the Elder]

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.

HAL

(This warranty gives you specific legal rights, which may vary from Whizzer to Whizzer)

 

[KilroyCD]

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.

HAL

(This warranty gives you specific legal rights, which may vary from Whizzer to Whizzer)

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.

 

[Hal the Elder]

HEY KILROY:

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.

HAL