KymcoForum.com
Scooters - 125 to 300 => Yager GT 200i => Topic started by: Zimmerman on October 24, 2012, 10:45:54 AM
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I bought this 2010 Yager with only 295 miles on it.
I've gently put 50 miles on it as it still needs to be broken in and I'm getting to know this scooter.
( I've logged many hours on Riva 180 & 125 as well as People 150.)
This Yager scoot has significant vibration at 50 to 60 MPH. I've not gone over 60 MPH yet.
I guess the vibration must be 'up/down' or a general vibration because I don't feel it side to side.
It does not seem to be RPM related.
I don't feel it particularly in the steering.
Has anyone had this type of problem, and how did you isolate the cause?
I wish I could run the scoot on some type of Dyno-belt so I could see what's happening . . . For now I'll have a few friends look at the wheel while I'm driving the scoot.
Kevin
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I just saw this info about dyna beads balancing tires.
Is there any down side to trying this ?
http://www.innovativebalancing.com/motorcycle.htm (http://www.innovativebalancing.com/motorcycle.htm)
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Sounds like tire balance to me. They are balanced at the factory, maybe you threw a
weight? Or one tire could have a lump in it (factory defect).
At certain speeds mine gets harmonic rotating vibrations but they go away at
faster or slower speeds. That's just the nature of a scooter I think.
Not sure a local shop could/would balance them for you. The bike is covered by a 2 year warranty
though my dealer is a tiny shop with no balancing equipment that I could see. Bring it to a dealer
and maybe they would put a new tire on (or balance it). (if it's still in warranty).
Dyna beads work for some people. Motorcycle Consumer News did a test of them a while back
and determined they did not do as good of a job as a "proper" balancing. They would be difficult
to get into the tire. I have trouble getting my air pressure gauge on those stems.
One last thought. The suspension might be oscillating. Try adjusting the rear preload stiffer and
see if it changes anything.
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Randy,
That's a good idea - I'll adj the suspension & pst the results.
Kevin
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I vote for a wheel out of balance although you did not say specifically the vibration was road speed related only 50-60 mph. I have good experience with Dyna Beads in scooters and related similar products in motorhome tires. Remove all factory weights before you put Dyna Beads in. The trouble with stick-on weights is they can and do fly off.
Karl
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Yep - the vibration starts at 50 MPH and continues up to 60 MPH.
I've not yet driven the scoot faster than 60 MPH, as I still breaking it in.
The vibration is not noticeable at any speed lower than 50 MPH.
I'll order dyna beads but try a few things while I wait for them to arrive.
It would be nice if the beads fixed it, but even if they 'change' the problem then that will confirm it's a tire balance issue.
Kevin
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Adjusted Rear Suspension - Vibration Changed
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Suspension Adjusted - Vibration Changed
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I adjusted the suspension as MotoRandy recommended.
It was at the 'lowest' setting which allowed the spring to uncompress as much as possible.
I assume the dealer [or previous owner] set it that way to give the smoothest ride ?
I only adjusted it one click 'shorter/firmer' but the vibration has changed/improved.
Now it doesn't start until 55 MPH and is less noticeable.
I will adj it one click at a time and take test rides . . . I'll let you guys know how it goes.
Kevin
PS:> I'm thinking this means the rear wheel is out of balance - the firmer suspension is just resisting it more.
I did order the Dyna Beads and will still put them in the tire.
Once the beads are installed, I'll put the suspension back where it was and take a test ride - just to see if the Dyna Beads have an effect.
I tried to attach a photo but the uploads folder is full. Here is a link to the photo in my flickr account.
http://www.flickr.com/photos/xriva18707/8124568703/# (http://www.flickr.com/photos/xriva18707/8124568703/#)
(http://www.flickr.com/photos/xriva18707/8124568703/)
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I've tried mine at each setting and never had a vibration. It must be something below the
shock. The only thing rotating faster with higher speeds is the wheel.
I took off my shocks yesterday (I was looking to improve their operation) and I did find the
exhaust side shock didn't align to the mounting holes. It seemed to be 1/4" short! I ended up
adding a washer under the mounting eye (vertically) and loosing up everything to try to match
side to side. Maybe now mine will vibrate now that one side is not forcibly compressed by the
other side?
The back shocks have horrible damping by the way. The springs should be stiffer and damping
should be softer but there is nothing you can do with the stockers...
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Just wanted to update the group - the vibration is still there.
It is a general vibration felt through the seat and floor - but not especially through the handle bars.
I adjusted the rear shocks hard, soft and in between - no effect - there is a noticeable vibration from 55MPG up to 60 MPH.
I've not driven the scoot over 60 MPH and it doesn't vibrate under 55 MPH.
It is enough of a vibration that I'm concerned about safety.
The front tire pressure was a little low - fixed that - same vibration.
Installed Dyan Beads - front and rear - same vibration.
Coasted down hill with engine off - only got up to 35 MPH - didn't hear/feel anything.
If I can find a big enough hill with a smooth road surface and little traffic - I may try coasting again @ 55+ MPH.
It's hard to hear with a full face helmet (if there is anything to be heard.)
The vibration seems to be MPH related rather than RPM related.
I say this because I run the engine at all RPMs as I accelerate - no there is no vibration until 55MPH.
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Any tips on how to isolate the cause (or eliminate possibilities) would be great.
How would a bad wheel bearing behave ?
Would it cause vibration at only higher speeds ?
How can I test for a bad bearing ?
What does drive belt slap feel like ?
It is speed related ?
How could I test for that ?
. . . Kevin
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I doubt a bearing would do that. The wheel does rotate faster as you speed up.
I think the top speed is 1750 RPM's at the wheel. A lumpy tire or out of round rim
might do it.
The belt slap is generally accelerating from a stop, you hear a rumble or thump
as the belt touches in the center between the 2 pulleys. All that happens at belt
speed so would go away as you max out the belt. It could happen when you let
off the throttle suddenly.
I guess a loose motor mount could cause vibration at high revs...?
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The problem is in the rear wheel / tire.
On the center stand at ~6500 RPM you can visibly see the wheel moving up and down. Also gently placing finger tips on either side of the wheel (near the bead) you can feel the wheel wobble side to side.
I'm going to rig up some static jigs so I can slowly rotate it by hand - using te jigs to 'see' the problem.
Testing ideas welcome . . .
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Well the manual says it's one of 3 things;
Bent Rim
Faulty Tire
Axle not tight
Your allowed 2 mm runout max. So if you can see it...
Try putting bike on center stand and wiggle rear wheel.
If it wiggles it's the bushing/bearing or loose axle bolt...
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Thanks Randy - I'll try that and let you guys know.
Also I'm going to rig up a static jig - I'll use it to closely inspect for bumps on the wheel or tire while slowly turning it by hand.
Forgot to mention, tests done in my last post were also done on our People 150. The P150 had no wobble.
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I grabbed the rear and tried to wiggle it - no movement - it seems solid.
Laying a ruler on the floor and spinning the rear tire by hand - eye balling the ruler and tire - I can see there is some side to side tire movement.
I'll have a dial indicator this weekend and will quantify that movement.
I've also noticed the rear disc break seems to rub a little and not consistently / evenly. When I spin the tire by hand sometimes it continues the drift a bit, other times it stops drifting almost immediately. It depends on where in the rotation the wheel (brake) is. This appears to be caused by the brake rubbing and not evenly.
I would think the brake shouldn't rub at all.
But the unevenness implies that the brake pads and disc are not 'square' to each other.
I will be checking that the axel / wheel is square. (if it's not square that would also explain the brake.)
Feedback welcome
Question: When the scoot is 'assembled' by the dealer does the rear wheel get mounted, aligned or checked then . . . or is that done in the factory?
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Very few brakes do not rub a bit, especially as they get older and stuck in place. Though
rubbing then skipping might say somethings crooked.
I have 2 bikes in my cellar "shop" right now. The older BMW rubs for 1/4 or less of the
total rotation as the rear wheel is rotated. The Yager drags all the time (not sure if it's
the brake or the heavy mass of the clutch).
Some setups have "V" shaped clips that go over the top of the pads to hold them apart.
I would doubt the rubbing brake would create vibration only at high speeds but you could
remove the pads and ride it. Just don't grab the brake! Tie a bright ribbon around it to
remind you!
If the rear tire wobbles it's not clear from the manual what could be bad. It shows a long
collar going into the wheel and some spline's on the shaft. And it's supported on the outside
by the swing arm. It looks that if the collar was short or axle nut loose it could wobble.
I imagine one could bend the rim not sure what they are made of or how brittle the are...
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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 ?)
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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.
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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.
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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.
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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. ;D
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.
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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.
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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 (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 (http://www.ebcbrakes.com/automotive_product_news/diagnosing_problems_brakes.shtml)
And
http://www.totalmotorcycle.com/maintenance/brakes.htm (http://www.totalmotorcycle.com/maintenance/brakes.htm)
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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?