Modern Vespa

I have tried to get it to do it: all kinds of combinations of high speeds, constant speeds, decelerating, one-handed, no-handed, etc. and I cannot get it to shake. How about you'all?
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OK, I followed directions & tried some more to do it, but it wasn't interested in dancing.
So, is the 300 GTS less prone to this?
The limited responses seem to indicate maybe yes, but this is a small sampling.

Possible factors:
1. the 300s seem to ride on Pirelli GTS tires: could be stiffer and resistant to lateral movement; different weight & diameter means unique centrifugal and right-hand-rule forces.
2. the front suspension of the 300 might be different (shock/spring)--not just colored different: absorbing aberrant energy in front end (?).
3. I have a medium sized windscreen: lots more pressure on the top end.
4. I have a racing stripe on my fender! nuffsaid

not advising you to do this, but if you so choose then go for it. Get bike up to about 40mph and then take your left hand off the bar, and then roll the throttle completely off. Good luck.

Have not had a problem. If I hit a rough spot in the road, then a little wobble.

What tires are being delivered with the 300 Supers currently?

From what I have seen at my local dealer, they come with Pirelli's...front and rear Pirellis...dealer says they are good tires but don't last for shit....short lifespan....as usually is the case with good performance tires...that's why I went with the Zippy's at replacement time...tired of shelling out money for tires too often.

Just once. Must have been the right circumstance. My trade-in 250 exhibited quite a bit of wobble. Except for that one occasion, the 300 does not display the same tendencies. (I have a Vespa top box with the associated heavier bar ends installed.)

The speed Rating on the Zippys is not enough for a GTS 300 ! You are flirting with a potential problem.

I've been fairly happy with the Pirellis, and I only noticed a tiny bit of wobble when I let go while decelerating, but it was barely noticeable. I haven't tried it since I got my topcase mounted last week, I'll have to test that out.

The biggest complaint I have about the Pirellis is that they seem to be a little slippy when they get nice and hot. I stressed mine pretty good on the Livermore ride during Amerivespa. The rear is pretty well worn out after about 3300 miles though, which is about typical for most tires I've tried. However, I would be surprised if the Zippys would last much longer. The Zippys for the GTS are L-rated, which is good for 120kmh (75 mph), so I wouldn't worry too much about running them on a 300, unless you're riding WFO for long periods of time. From what I've seen though, the Zippys' relatively soft compound generally doesn't last for more than 3000-3500 miles. The best tires I've found are the Heidenau K61's, hands down. They're extremely durable and I've seen rears that have lasted more than 6000 miles. They feel solid, they're quiet and they handle really well. I've been very happy with the set on my 250 and I'll be putting one on the rear of my 300 very soon.

Bagel, any comments on the wet grip of those Pirellis? I have Pirellis, I think they're a SL 32 or 23 or something and I HATE their wet grip, they suck and they wear fast.

are we talking about under braking, or you are sliding around wet corners like Valentino Rossi at Silverstone? I don't understand when people complain about grip. Most of us don't routinely lock up our wheels, nor do we drift through corners, nor do we regularly come close to doing either, so I am never sure what they mean by grip.

I don't know what you mean by "they suck". I don't have much experience, but a lot of the limitation of the GTS handling has a lot to do with the small wheels and not the tires. I rode Kymco 250s with 16" wheels, and they corner like sportbikes in comparison to my GTS.

In comparison to the OEM Savas the Pirellis do not hold as well when turning, in particular when the road is wet. That is my opinion having ridden with them numerous times in the rain.

Is the wheel size on the 300 a 12?

The tires that came on my 300 are Pirelli GTS 23 (front) and GTS 24 (rear). They may be different from the SL's you tried, but I'm not familiar with them, so I can't say for sure. The only time I rode in the rain was shortly after I got the bike, and I was careful not to push them too hard, being new tires, but they seemed reasonably decent to me. They did wear faster than I would have liked, but I expected that.

As far as the "grip" goes, I felt them starting to slip slightly as I was going through the hot, dry, twisty mountain roads between 30-60mph. No locking up wheels or drifting - DRIFT UNIT! - just pushing it a bit in the curves and corners, though not enough to scrape the center stand. It was enough to make me feel slightly less than confident in their abilities, and I felt much more comfortable when I rode my 250 with Heidenau K61's on it.

The tires I thought sucked ass were Michelin Pilots, Sport or City, they didn't grip for shit when cornering and I felt the rear slipping even under normal cornering on dry roads. My understanding is that Michelin uses the exact same compound for all of their scooter tires, just a different tread pattern, go figure. I never ride anything with big wheels, so I'm only comparing apples to apples, not apples to oranges. Personally, I'm sold on the Heidenau K61's (or K66's for inclement weather), they're the best tires I've ever ridden on... forget the K58's though, they're way too loud and soft, and although I thought they handled ok, they don't last longer than any other scooter tire I've run.

Yup, 120/70-12 and 130/70-12, same as the 200 & 250.

Not true, some are dual compound, some are multi-compound. MGS in particular are very well tweaked for their target market.

MPS - very grippy, not so long life.
MPC - harder centre bit, meant to prolong 'upright' life for commuters.

Horses for courses folks.

Just a thought from the motorcycle world...problems with the front end can sometimes come from the rear of the bike. Head shake can be sorted (sometimes) by dialing in a little more preload in the rear shock(s).

Other times the rider is actually a little too stiff on the bars, and can unknowingly feed the energy from bumps and such back into the bars causing a bit of a shake. Relax your shoulders, don't be stiff.

Scooters seem to have a real rearward weight bias, so I'm willing to bet stiffening up the rear suspension in small increments might be a place to start (if that's even possible..stiffer spring...more preload...new shock?).

The fact that it happens on decel stumps my though....that and my relative lack of "vespa" experience.

Does it happen when you just roll off the throttle and don't touch the brakes? I'd try it, with no brakes....just the rear...just the front...then both...just to gauge things.

I tried it out on my 300 yesterday and I confirmed that there is definitely a good amount of wobble between 25-30mph when I take my hands off the bars. I don't notice it at all when my hands are on the bars, but I haven't tried it one handed, while applying one of the brakes. I'll give that a try. It doesn't seem to have much to do with accelerating or decelerating, or riding style or position, it's just a vibration that occurs at a certain speed range that's inherent with all GTS's (and GT's too, I imagine).

Your point about the rear preload is a good one, I think my shocks are set at the lowest setting, or possibly one notch up. I'll try adjusting them to see if that makes any difference & report back.

Again, I'm certainly no scooter expert, and I'll have to see what mine does just for giggles.

Like some others have said, tires could make a difference, as could something as simple at checking your tire pressure.

Soooo...I'd check my tire pressure. Put a click more of preload on the rear shocks. Then try your experiment again. It could just be the nature of smallish wheels, a lot of rearward bias of weight (you included), that just makes the front a bit light on its toes.

I was thinking you felt the wobble while your hands where firmly on the bars. If it's only happening "hands-free" it could just be a very flighty front end tracking imperfections in the road.

My guesswork thoughts on braking affecting things, is...the rear brake only test "might" lighten up the front enough to see it wobble more. So add some rear preload. The front brake only test should load up the front and stop the wobble. So again, more preload at the rear.

While your cruising around getting a feel for things you might also see how it feels if you shift your weight more forward on the bike...which should calm the front down too.

It also might be you've thrown a wheel weight and your front wheel is out of balance. With such small wheels.

Lots of ideas, and no answers.