Modern Vespa

I am new to the Vespa world. I recently purchased a 2010 Vespa GTS 300 Super Sport. It runs and drives great but the PO mentioned that he had a modification done by a local shop that allowed for more low end torque for improved "takeoff". He mentioned that the mod has hurt the top end speed. Well, I thought I'd be ok living with this mod but have since determined that it has significantly hurt the top end speed. While its very sporty off the line, I can barely get over 55 mph.

Can anyone help me understand what modification was likely done? Or maybe be able to check to see if some particular mods have been done. I'd ordinarily search for gearing mods or clutch mods but I haven't been able to find much.

Thanks in advance.

not sure if these are up gear or down gear but could be one of these (note these two are different ratios one is 22/45 and the other 15/49)

https://www.malossistore.asia/en/secondary-gears-htq-z-22-45-vespa-gts-super-300-ie-4t-lc-euro-3-2013-quasar-m454m-6714844-vegt300-M-P
or
https://www.sip-scootershop.com/en/product/gearbox-15-49-teeth-polini-primary_P2021413


could maybe also be different roller weights

Because you said you're new to Vespas and I want to err on the side of "just in case you don't know..."
Start with the roller weights. It's MUCH easier to check the transmission (weights and springs) than the primary drive gears.

Roller weights were my immediate thought. That is the most common modification to change acceleration or top end.

Second would be improperly installed Dr Pulley slider. Install them backwards and you get a top end limit around 50-55. Don't ask me how I know.

Yeah, roller / slider weights first.

Could be gearing, but that's advanced stuff.

Thanks for all of the responses.

I am certain it was the weights that he mentioned changing.

Is achieving higher top end speed as easy as re-installing the factory parts? Does anyone know the size of the factory weights...or maybe a part number?

I have seen factory stated top speed for this bike at 75 mph. Were these typically accurate or overstated? I don't necessarily need to get to 75 but I'd sure like to get to 65.

Yes, I believe it should only be necessary to install stock size rollers and sliders assuming nothing else was changed.

I don't know if all Vespas are about the same, but figure about 7% difference in actual over display for mine, so 75 is about 70 mph.

Is there anyway you can contact the PO before taking it apart to get an idea of exactly what mods were done? Even with a rollers/gearing change, it should get over 55 easily.

I get 82-84 by GPS with stock roller. The only time I ever has an issue with any GTS I have owned not getting over 65-70mph was when one had a cracked fuel injector. If i couldn't get to 75 I'd want to know why. Which is how the cracked injector was found.

A full service with OEM belt, rollers, variation glides should return you to stock performance unless there was gearing changed which is not likely. You can order a kit with all you need from Scooterwest, AF1Racing or ScooterPartsCo in the US or SIP in Germany.

part number is 849480 (6 of these). these are an easy change and will restore your top speed if nothing else was changed (although with such a large drop in top speed I am suspicious of more changes)

https://scooterpartsco.com/030-piaggio-c-801_836/piaggio-roller-weighs-for-gts-300-p-9197


A healthy normal GTS will reach approx 75mph GPS or 85mph Speedo (or more depending on things*). My 2019 supertech exaggerates by approx 8-9% depending on tire model, pressure, wear etc.



* eg my 2009 300 didn't seem to have a limiter and reached higher top speed than my 2019 supertech which definitely has a limter

I will just add that getting up to top TOP speed on a GTS requires some... finesse. You won't achieve it going up an incline or riding into a headwind. You might have to tuck down to present a smaller aero profile. And you often have to work up to top speed, coaxing the bike, especially if the rev limiter is kicking in.

It's an art form and a skill unto itself.

and/or loose some weight

It's not like you to be lost for words

and a windscreen (small/mid?) should help aero a bit

I'm speechless

fear not, I'm confident that your voice will return

I can't think of a way you could get a GTS 300 to 55 mph by changing to lighter weights. Unless you're burying the tachometer at 55 mph, it's probably more than just that. Even if you dropped down to 9 grams, the bike should still hit the mid to high 60s. Have you compared it to any other Vespa 300s in terms of the quickness he claims to have achieved? My suspicion is that it's not doing much more than a stock 300.
Getting a GTS 300 to top out at 55 mph requires a very special kind of tuning expertise. Modifying the airbox so it gets tons more air than it was ever designed to is one of those dumb modifications that can achieve these results. The ECU stops reading the O2 sensor at about 6K rpms, and can't adjust the air fuel mixture to compensate, so if it's getting way too much air above that, it might seriously bog, but that's usually pod filter territory.
If you can't figure it out, take it to Kyle.

that's why I'm still suspecting that it's also got a gearing change.

Except that every gearing kit I am aware of is used to get higher speeds out of tuned motors. You lose takeoff. Unless someone stuck GTS 300 labels on an LX 150, I can't think of any mod that would slow it down that much.
The OP says a shop did the "modification." Can anyone think of a single person who would have left a shop with a GTS 300 that went 55 mph, and didn't go right back to ask what the heck happened to their bike?

Thanks everyone. Parts have been ordered.

With that said, it does feel like there is a rev limiter/governor engaging when I am approaching 55 mph. Will that self adjust with these new roller weights?

Yes. If you feel something start to happen to slow the bike down as you get close to 55, the engine is probably getting ready to adjust itself in such a manner that your fuel consumption will drop dramatically. After that, it'll go about as fast as your buddy's pickup.

There is not a shop in the US that would modify a GTS so it buried the tach at 55.

Are you sure about that? I mean, like, really sure?

I'm not even sure what would accomplish that. Flat tires? There aren't gears tall enough, and 9 gram rollers might take 5 mph off. But anyone who got their bike back from the shop 25 mph slower is going to ask them to put it back to how it was before they fixed it. It's a 2010, so I'm guessing there's brass in the oil.