Modern Vespa

I've been wanting to see this for a while, can't wait for a kit to come out.

https://www.motorradonline.de/umbauten-und-einzelstuecke/kompressor-vespa-gts-300-im-einzeltest.803514.html

https://www.roller-motorradbox.de/

Do youknow any prince,just for the kit

The only challenge with a modification like this is the balance of the bike. What I mean by this is the power, suspension and brakes need to be in balance.

The stock 300 or 250 power is good for this sized bike. Good enough that I would change suspension then brakes, then power in that order if I was making modifications. I have always felt the brakes on the bike are the limiting factor as you can only get so big of a disc up front. You can do some other things to the brakes, but you are limited to a max of maybe a single 240mm disc because of the diameter of the wheel/front suspension layout.

If you bump the power up with a supercharger (or turbo), you are going to have lots of power but will your brakes be up to the task? Will the suspension?

If you want the extra power, start making the suspension then brake mods now and you will be ready when the kit comes...

Jerry

Can go bigger wheels and bigger disks.

Yes, but not big enough to accommodate a 300mm disc. Stock is 220mm; I have heard of a 240mm project. Is there a larger diameter out there?

You can get a big improvement to the brakes without fitting a bigger disc, by fitting Brembo or Frando callipers.

Mike

Not sure what size this is, but I would bet that a 260mm would fit inside of a 13" rim. I know for sure 250mm fits: https://www.sip-scootershop.com/main/base/Details.aspx?ProductNumber=m6213085&_language=en

Caliper mounting is another issue, but I think it's safe to say that braking could be substantially improved.

Top speed should be about 98.5 mph if equipped with stock gearing & 13" wheels, so braking should probably receive some attention anyway...

All this discussion is relevant for the factory engineers too; I am sure they are or have looked into the future model line to figure out how far can they take the "iconic" style into the future.

Power (engine) upgrade is the most straight forward change. This shouldn't be an issue.

Suspension, the front in particular, is an interesting challenge. The current design backs into the original design which has its linkage into its aeronautical past (nose gear/suspension). I think that design may not scale well to larger diameter wheels. If 13" is the max now, can it be pushed to 14" The answer is, yes it can, but there will be issues to contend with if the engine is pushed to a true 300cc (or slightly larger). The front will have to get more beefier. On an aircraft, this isn't too big of a deal but for a bike who lives on the ground, getting the unsprung mass up isn't a desirable path. It is easily solved by going to a traditional front suspension but will it detract from the "Vespa look" too much?

Brake upgrades is the toughest issue because the smaller diameter wheel is a very real limiting factor. To really upgrade the brakes, you will have to go to a bigger diameter wheel.

So, my guess is we will get one more upgrade designed and built around 14" wheels... We should get a real 300cc or something slightly larger. The body will have to scale a bit but it will "look" like a Vespa. And we will flock to it - or some/many will! I will stay with my 2016 Primavera 150. Its a great in-town scoot. The more powerful Italian bike will be the BV350.

Spacetiger, have you ever tried Brembo or Frando callipers? They do make a significant difference. With a Brembo in front, you can do with one finger what usually involves your whole hand. Don't need bigger wheels and disc for a good improvement.

Mike

I keep saying that the next power upgrade is to put the BV350 powertrain into a metal unibody small-wheel bike. It'll have to look like a Lambretta in order to get the engine package to fit, and I'm not sure Pigaggio is willing to go there (though the 946 and Sprint/Primavera are visually going in that direction). Changing the aft section (at least) of the bike will probably break accessory continuity (racks, crashbars, seats) and definitely require redoing the production line -- including the massive steel presses used to make the unibodies. Expensive.

Mike,

I have [mostly] experience with NISSIN fixed calipers; I consider them clones of the ones you cite. The biggest advantage of these calipers if matched properly to the master cylinder is the much greater pressure you can generate vs sliding calipers. You can change the pads to ones with higher coefficient of friction to translate that greater clamping force into better stopping ability - but never forget the leverage of the smaller disc is a limiting factor. You can generate much greater pressures to increase stopping ability, but the current components of the scooter braking system are really pushed by the higher pressures. I can see on my BV350 brake project the MC flex when max pressure is generated. The caliper also flexes.

For a stock 300, this brake upgrade is a noticeable change improvement. But when you add 50% more power and change the top speed to be in the mid to upper 90's you are pushing the machine in a different riding envelope. Look at the latest 250-350cc sportbikes. They weight about what the 300 weighs and have the power to get to 90-105. They all have single front discs in the 296-310mm range. Even then, the riders that push the bike are looking for more braking ability. Can you imagine if those bikes only came with 240 or 250 mm discs?

If you slipped a 220-240mm disc on the BV350, you could experience what a more powerful 300 would be like with a stock/near stock brake set up.

The whole point of the discussion that I think we all agree on is that the brakes (and suspension) needs to be upgraded to cope with the increase in power.

I look forward to some one writing up their experience with making the changes. It would be a hoot of a hotrod.

JErry

Anyone know who sells a carbon front fender for a GTS like the one pictured? Thanks

I'm not sure it is real carbon fiber. Probably just hydro dip.

Back to the original point of this thread... check out the belt setup.



The supercharger appears to be a Rotrex C8-6:

Apparently, the lower crankshaft pulley is too large (or the blower pulley too small). According to the article they had to limit the RPM to 9400 (which maxes out the supercharger RPM @ 240,000)

According to the article:
"Price : Complete vehicle: 18,666 euros; all tuning parts also available separately, prices are available on request"

The upper pulley is not a pulley,it is a belt tensioner.The upper pulley attaches to the compressor and is hidden behind.

I use Rotrex on my Kawasaki since 2010,it's a good unit.

I would guess a brembo or other caliper would be somewhat of an improvement. Im guessing you still run stock pads in those?

The only way Im adding more braking power to my large frame is going to be with a conventional front fork... like off an SR50. Those come with 13" wheels. The stock link suspension does not like to be leaned on hard when on the side of the tire. Its not just me who noticed this.

I can't read German: I would also like more information on that interesting setup - Kit? Where? How much?

Try using Google Chrome, it auto-translates. https://translate.google.com/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=https%3A%2F%2Fwww.motorradonline.de%2Fumbauten-und-einzelstuecke%2Fkompressor-vespa-gts-300-im-einzeltest.803514.html&edit-text=&act=url

From the article: "Price : Complete vehicle: 18,666 euros; all tuning parts also available separately, prices are available on request"

Okay!

Thanx - that is way too much for a fast scooter

That's a LOT of money to add to the price of the scooter plus all the additional parts that are implied... This kind of speed is not for me anyway, but I found the technical discussion regarding necessary considerations when adding more power here interesting and very informative.

Sorry if I'm going a little off topic, but I am reminded of an amazing scooter I saw last year in Greece. Supposed to be the fastest factory scooter available, was designed and built by Piaggio in Pontedera, I think only for a few years starting in 2007. The Gilera GP800 with 75HP , wheels are 15" in back and 16" in front:

And it definitely doesn't look much like any Vespa. Here's a review that sounds like it could have been written by Piaggio, but contains lots of technical detail: https://www.topspeed.com/motorcycles/motorcycle-reviews/gilera/2008-gilera-gp-800-ar52639.html where I found this brake info: Just for fun I checked & found 3 for sale in the UK for ~$5500 - $6500, kinda want, maybe just for a day 8)

Terry, the GP was a great scooter with almost zero problems. I have 3 customers in Veria, that still have them. Amazing power and torque but a bit ugly to my taste. The Gilera brand unfortunately is killed by Piaggio and the rebranded GP was the Aprilia SRV 850. Now, that is a great looking scooter. There is a GP 800 Turbo in Athens. Crazy guys, the ones that built it...

More technical details: 42 HP at the rear wheel @ 0.8 bar (11.6 psi)

Torque should be at least 24 ft-lbs, assuming peak HP occurs at its 9400 rpm redline (although... who knows what the power curve looks like now.)

https://www.ebay-kleinanzeigen.de/s-anzeige/gts-300ie-super-abs-kompressor-lesen-lesen-/846804631-305-9305

Last edited by AnnDee4444 on Tue, 15 May 2018 16:14:39 +0000; edited 1 time

You can see the upper pulley in this photo. It is roughly the same size as the tensioner:



Dynagrego, was that a kit or did you fabricate everything?