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Author Topic: Shimmy, Shimmy, Shake, Shake  (Read 2853 times)
Expat47
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« on: October 16, 2016, 08:43:46 »

Ever since I've had the 350ie it has started shaking or vibrating around 130kph (81mph) depending on the direction of the prevailing wind. If it were a constant vibration I'd start looking at loose parts, tyre (almost spelled it with an "i") balance, etc but it's not! The vibration seems to come from some built up tension then released in a single, short burst before going back to smooth riding. These areas of calm and vibration last only a second or so.

I've tried specific runs with and without the 50l bucket on the back... no difference.
Tire (50/50 on spelling is only fair) pressure is correct.
It's not the windshield (windscreen) or the mirrors that I can tell.

Anyone have the same problem? A solution? A suggestion on where to look next?

Thanks (Cheers),

Don
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Don
Dave Milnes
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« Reply #1 on: October 16, 2016, 10:08:22 »

If it were a regular resonance at exactly the same speed/revs regardless of wind conditions I'd say it was a mechanical issue around a sonic resonance caused by a balance or even an engine intake/exhaust resonance or even a belt vibration, but as it is dependent on wind direction this would point more towards an aerodynamic issue.
You have already tried the top box and it wasn't that so try without the screen, you never know they can have odd side effects. Try ducking down low yourself or sitting taller, further back or forward as it may be it's you that is the aerodynamic problem.
Also does the X10 scoop air into the fairing anywhere except the radiator, and has it got ways to vent this pressure sufficient at high speeds into a head wind? Could be something simple.
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Mike H
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« Reply #2 on: October 16, 2016, 12:55:28 »

Have never experienced this, and have had it flat out a few times. Been blown about by wind tho a few times but that's not at all the same thing.

Is bike new or second-hand?

Grasping at straws, possible ideas are play in swingarm pivots, fork clamps and/or front wheel spindle loose, or wear in the sliders, so forks are twisting/flexing, that kind of thing. (I have experienced this on a Moto Guzzi Spada years ago, it caused suicidal high-speed weaving!)

If bike is second-hand, has it been in a previous accident of some sort? Has anyone disturbed the suspension / steering for any reason?

Re tyre pressures, OK, but is your pressure gauge accurate? I bought a new one few month ago and found I'd possibly been keeping all my tyres too soft! Also it confirmed that my 40 years old pocket type 'pop-out' gauge was probably still accurate after all.


Try ducking down low yourself or sitting taller, further back or forward as it may be it's you that is the aerodynamic problem.

Possible. The classic cure for stopping a high speed weave was lying down forwards (aka, lying on the tank, but not applicable to a scooter!)


Quote
Also does the X10 scoop air into the fairing anywhere except the radiator, and has it got ways to vent this pressure sufficient at high speeds into a head wind? Could be something simple.

There are two very small vents on either side of the fairing and below the headlamps unit, but purely for decoration as far as I can see.

There is a gap below front edge of screen, where the Piaggio badge is, so that air blows up the inside of the screen as well as the outside, presumably to reduce turbulence around the rider's head. The standard* screen itself is not too large in area and quite narrow so can't see how that could be causing the problem TBH.


* which raises the question, is the screen the factory standard one or something different?




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Mike H
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« Reply #3 on: October 16, 2016, 13:01:19 »

NB: tyre pressures are 2.3 bar front, 2.4 bar rear (solo riding), BUT that is Piaggio's figures, not necessarily same as tyre manufacturer's recommendation, so another thing you cn try is increasing the pressures a bit.
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Expat47
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« Reply #4 on: October 16, 2016, 13:19:56 »

It was purchased new back in Nov of 2012 and has had this effect ever since then. I've just had the 20k service so the belt and sliders are new but the problem presented back in 2012 also so...

I keep the tyres as 2.5 and 2.6 as I'm riding with the bucket on the back and weigh in at 115kg (18 stone). Once the wife gets on we're at max load but I don't think I can't remember if we've ever been on the highway two-up.

There are the vents in front (as mentioned) and two more by the passenger floorboard.

This really isn't a problem, as far as problems go, as I don't to a lot of highway riding and the vibrations present no handling problems at all. It's just starting to get under my skin because I can't figure out what's going on.
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Don
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« Reply #5 on: October 17, 2016, 07:48:40 »

Are you certain that the traction control isn't kicking in when you hit a bump or a rough patch of road? That's the only thing that unsettled mine but you should see the light flicker briefly when that happens. It might be out of calibration and therefore over sensitive.
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« Reply #6 on: October 17, 2016, 10:26:52 »

Are you not supposed to do a calibration if the tyres have been changed as well?

What about the rev limiter?
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'04 X9 500 Evo in YELLOW - LED's, K&N, twin lights, bleepers...
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Expat47
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« Reply #7 on: October 17, 2016, 14:20:55 »

Are you certain that the traction control isn't kicking in when you hit a bump or a rough patch of road? That's the only thing that unsettled mine but you should see the light flicker briefly when that happens. It might be out of calibration and therefore over sensitive.
No, this is a constant thing as long as I'm going over 125kph or so... smooth roadway.


Are you not supposed to do a calibration if the tyres have been changed as well?

What about the rev limiter?

Haven't changed tires. That's coming up next spring.
I'm 99.837%* sure it's not an engine issue.

*96.3% of all statistics are made up on the spot.
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Don
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