Vibration above 50 MPH - Yager w/ only 350 Miles

[Zimmerman]

Ok the digital dial indicator says:

Yager
Wheel (near bead) varied from -0.40mm to +0.53mm
Tire (side wall) -0.63mm to +0.1mm

People 150 (doesn't have a problem - used for comparison.)
Wheel -0.13 to +0.1mm
Tire 0mm to -0.38mm

Randy said the run out spec was 2mm - both these scoots are within that spec, but the P150 is tighter.

Next I'll check to see if the rear wheel is mounted perfectly on axis with the center of the bike.

(This may just be a defective rear tire, but I like to be sure before doing the work.  It's a bear getting the rear tire off of a People 150.  Is the Yager just as bad ?)

[Zimmerman]

Ok this is interesting and unexpected.

I took the rear  brake ass'y off and secured it to the muffler stand offs.
I ran the scoot on the center stand - just looking at the rear wheel, it still appears to be bouncing.
No surprise there, I didn't particularly think this was a brake problem.

The surprising thing was, when I took it for a test drive ( without a rear brake ) I went as fast as 65 MPH without any vibration.
.
Later I'll use the dial indicator the check the braking disc for run out.

If that's good then I think the side to side movement of the wheel/tire is more than the uncompressed brake pads can handle.  Apparently the disc is hitting the pads enough to cause vibration.

[az_slynch]

Interesting. I've noted that the front pads drag a little if I release the brake  lever gently. If I flick the lever forward after braking, the pads won't drag. The mechanic at the shop I bought my Yager from said that it would happen until everything broke in, but I'm a bit skeptical. Only 175 miles so far, though. Waiting on a sprained ankle to sort out before getting on the scoot again.

[Zimmerman]

Az

As a brother in Scootering, let me offer to ride your Yager while the ankle heals.
Really, it's the least I could do.

The info you shared about your front brake got me thinking.
My rear brake fluid is completely full (topped off.)
There is no visible air bubble.

My front brake does have a small bubble - which is what I've always seen on other bikes.

I don't know if that matters or not - opinions anyone ?

The owners manual (page 56) recommends it be above the imaginary "L" mark.
But there is not a cautionary note to not over fill it.

(My coolant resivior is also completely full.  I've been meaning to remove some to get it down to the "full" mark.)

About the brake correctly returning to an uncompressed / unused position . . . I'll experiment on my scoots and post the results.

My Yager has ~630 miles on it.  But it hasn't had it's first maintenance yet.

[MotoRandy123]

A little extra fluid might cause a problem but those reservoir's are tiny,
it's hard to be accurate in filling them. You might be on to something as
 both of mine have bubbles. Can't hurt to take a little out.

 I remember filling mine all the way up on other bikes without a problem.
There is a rubber bladder in there to take up some space, it can collapse
to allow more room. But if you fill the bladder there wouldn't be any extra
space for expansion when it gets hot.

[Zimmerman]

Gents,

Here is at least one opinion that over full brake fluid resiviors will cause the pads to rub on the disc.

http://www.speedzilla.com/forums/ducati-supersport/3636-too-much-brake-fluid.html

More general brake info:

http://www.ebcbrakes.com/automotive_product_news/diagnosing_problems_brakes.shtml

And

http://www.totalmotorcycle.com/maintenance/brakes.htm

[mrbios]

I bought my 2005 Kymco Grand Vista / Grand Dink 250cc scooter 2 years ago with 2600 miles on it.  At about 8K miles the scooter developed a high speed vibration.  I concluded that the problem is the belt is worn.  Belts wear unevenly the same way drive chains wear on motorcycles.  That is to say the the belt is tight in one spot and as you rotate the wheel gets loose and the wheel is easier to move. It is mainly noticeable at high speeds above 60 mph.  It is a constant rhythmic vibration. You can feel it by putting the scooter on the center stand and rotating the rear wheel - hard to turn , easy to turn then hard then easy.  I now have 10K and am getting ready to replace the belt.  It cost $83 at the dealer. I'm not sure why you scooter would have this problem at such low miles – unless it got really hot due to slow driving where the scooter is barely moving on a hill and not fully engaged so the belt is slipping and so is the clutch.

Try putting your scooter on the center stand and rotating the rear wheel.  Is it easy to turn or is it like my scoot - easy, then hard?  Any updates to your problem?