Modern Vespa

Not sure if this should be called 'wobble' too, but currently I experience quite some steer/head shaking doing top speed with my GTS on the freeway. This happens on speedo speed 130 kmh / 90 mph...depending on the road surface somehow I think.

This instability looks worse than before...it is so' noticeable' it makes me slow down.
I can think of two reasons that have changed recently:

1. I installed the heavy barends that came with the Vespa Topcase. I had the original smaller ones for a while together with the topcase fitted.

2. Changed from Vespa large screen to Vespa small 'flyscreen'

I check tire pressure from the Sava's regulary.
My suspect the heavier barends the most...
I already thought they gave me some slight wobble on slower speeds too.

Any comments, idea's

the barends shouldn't give you a wobble. they should do the opposite. did you have a load in the topcase?

i imagine that the vespa should be more stable with the flyscreen as well.

I would think heavier barend = better
I also would think high screen would be more 'wind sensitive'

Topcase is empty, as it was with earlier rides.

The bar ends will change the frequency but they do nothing to remove energy from the system.

How's your front shock? push down hard on the bars, how long does it take to come back up to full height? does it overshoot and top out the shock when coming back up?

Well, maybe you should just speed up.

I had a similar situation on a motorcycle of mine, I added a topcase and got a wobble in the steering. I tried different bar ends, messing with the rear shock preload, adjusting the tire pressure etc... this went on for a couple of months. Then the wobble began to get more severe so I got serious about the cause. A maladjusted steering head bearing was the cause, it was too loose, a new bearing set and the proper torque on the ringnut fixed it right up. Maybe your scoot rolled off the line late in the day and Luigi forgot to torque your head bearings adding heavier barends to a loose steering mechanism could, I not saying it would but it could, make the wobble more pronounced.

Good luck running that down, bad steering scares the crap outa me.

BTW I am assuming that vespas have steering bearings that can require maintenance. If they don't please ignore this post.

My GTS was build in summer hot July. I guess Margherita just walked along through the factory wearing a too short skirt so that Luigi and Giovanni dropped out their eyeballs

Not sure if i can blame them, but I will keep an 'eye' on the bearings for the next visit to my dealer.

Actually, I am wondering if a GTS should be fully STABLE when doing above 80 mph/120kmh in general?
Or is some 'duck wagging' kinda NORMAL for a GTS at this speed?

i'm with her .. go faster.

When you check the tire pressures regularly, how regular is "regular"...once a day / week or month?
If month, my bet it is the pressure. Not the bar ends or top box.

I am in with het too, I would if I could...but at 90 mph my 'Donna Rossa' is doing her utmost best

PS: 'Regular' tyre pressure checking means around every 2 weeks. Or before a long trip.

Pretty easy to do trial and error on this one. I'd start with taking the screen off and trying it then take the top case off and try it, then put the screen back on. Make sure you haven't dropped a balancing weight off one of your wheels too.

90 MPH on 12 inch wheels is just short of insane, if not there. I would suggest keeping your tire pressure correct and slowing down a little bit. All the gear in the world isn't going to help you at 90 MPH on a Vespa.

Good luck.

SDG

I had a similar problem (shaking of the steering whell - not wobble) and it was solved as soon as I replaced the Savas. The shaking on my Gts used to appear after 120 km/h.
Not sure that you have the same problem, but check your tires. Savas are really bad quality tyres..

Sounds like the same thing...and we even have same color GTS 8)

It is indeed not just bobbling but resonating/shaking to start at top speeds.
I have been considering changing the Sava's...but I 'should' wear them first.

I guess Heidenau's are the best replacement...

LOL, do you think there is a common "shaking" issue with vintage red Gts's?

My advice is not to wait for the Savas to wear. They are bad tyres. As soon as I changed them with Michelin Pilot City, all the shakings disappeared magically! Not to mention the huge improvement in handling on the slippery greek streets.
One member of our Vespa club was terrified from the serious shaking, just tofind out that his front Sava suddenly developed a huge bulge, while he was riding with 100 km/h.

Another vote for immediately getting your front end checked. Worn/loose steering head bearings, bent fork, misaligned fork in the triple clamp, or loose nut, poor wheel balance, worn wheel bearings, may cause the problem. Sometimes you can go through everything and still be left with a headshake. I would not delay the evaluation, I have seen people get pitched off from headshake problems that they ignored. Good luck!

Thanks all for the answers and advices 8)

Main thing is to know that a scooter like the GTS should NOT start to shake when riding at 'reasonable' speeds.

'Reasonable' would mean below / to the max 80 mph / 120 kmh (speedo speed thus real life is -10%)