Modern Vespa

Hello All,

I need some help please.
I just changed the belt and rollers on my 2020 GTS Super HPE this weekend.
I followed Robot's guide (from Scooterwest) on youtube. I had no issues, other than the slide set I ordered did not fit, so I just left the stock in place.

I have a major issue with high RPM and lower high end speed. I do not know why this is happening. I can only do about 95 KM/H before the speed cuts out. The RPM seems super high and seems like it does not change to a higher gear (if there are gears changing). If there are gears changing, that is what is seems like (no top gear), but in any case,  the RPM is high and I cannot drive on the freeway.

Before this work, I could drive at 120 KM/H on the motorway before the limit is reached.



Can you please advise if the rollers I put in, can cause this issue?

Did I mess something else up ?
Should I put the old stock rollers back in?

I cannot see another reason why this happens, but any advice on how this can happen is welcome.


Parts I ordered on SIP Scooter in Germany:

Belt: 005 PI009598 Belt PIAGGIO for Vespa GTS/GTS

Roller set:   007 SR211714 Variator Rollers DR. PULLEY

Slide set: 006 SR2017N0 Slide Set DR. PULLEY SP-N (did not fit).

The slide set I ordered did not fit, so I left the stock in place (after cleaning the dust).

Thanks in advance for any help.

Kind regards,
Richard

That's too large of a top speed loss for a change in roller weight but I don't have experience with Vespa. I'd try the old belt first. If that doesn't make it return to normal, put some new stock ramp plate sliders in. I noticed problems with after market ramp plate sliders fitting as well as OEM.
Sounds like the belt isn't moving out as far as what you replaced.

14g seems like a heavy choice for sliding rollers ... Why choose that weight?

Thank you both for the reply. Still hoping for for input.

It should be known that, if you haven't guessed already, I really do not know what I am doing. I have rebuilt MC and cars engines and have a good working mechanical mind, but this belt drive system stumps me a bit.

EDIT: I found a nice explanation on Modernvespa for how it works:
I would really like to understand the mechanics of the rollers, variator, belt, etc. If anyone can point me to some info on this, I would appreciate it.

Regarding, why I chose 14g roller, no answer. I was presented with the drop down menu on SIPs web page, and I thought it looked right for my GTS.
I do not know what the impact is using a heavy roller.
One ting that I did not like, or feel comfortable about, was the shape of the rollers. The stock ones I took out were round, but the Dr Pulley rollers I put in were only half round with a pointy side. I was worried I put them in wrong or something, but looking online, I found the right way, I hope.

Regarding the belt, again I used SIP's web page ordering based on my model number, and the belt seems to be the same.
So if the belt is 'not moving out' does that mean it is too small?
I wondered if I got it too tight somehow. It seemed like the belt was king of snug when I tightened the variator. I really wish I knew how this worked better.
If too tight, could this cause the high rpms and loss of top speed?
I know I could take it to a shop, but it is my Vespa and I would like to learn by doing and get the knowledge from this.

Thanks again for input.

If you're not confident about the orientation of the Dr P 'rollers', open up and check again. It's very, very easy for one or more of them to topple over when inserting the backing plate and variator. This would probably result in your experienced symptoms.

OK, I think I installed them upside down. I found a nice video from Mitch's Scooter Stuff showing how to install Dr Pulley Sliders. I am quite sure I installed the round side up when I placed them.
I will open it up on the weekend and try again.

As noted previously, I will open up and reset the sliders.
I would like to understand why there was a question as to why I used 14g rollers/sliders and that they seem too heavy.
I have attached SIP's part description showing 14gr.
This is why I ordered this weight.

If I should replace them, what weight should I choose for my 300 HPE?

Even though I now understand the viator a bit more, I am not sure I get what the weight impacts. Maybe that the lower weight causes higher revs before gear change ?

I was hoping to get a little more top speed on the motorway 125+Kmh, which I get normally, while maybe lowering my rpms. Not sure if this is possible.
At the same time, going at this speed for a longer time on small wheels is a bit scary.

The standard rollers are 14g and round. Although the rollers you bought are 14g, they are not round and behave very different.

Apples and oranges.

Thanks. I understand that they are different, and that I may have made a mistake.
I am hoping for a recommendation and I will order new and try to learn from this.

I think a popular choice would be 13g or even 12.5g for those sliding rollers.

But, don't take my word for it 😀

If your sliders are in backwards that can cause the symptoms you are experiencing. I-2 oz lighter than round rollers are generally where most folks find sliders perform best from reports I've seen.

I use 13.5g with an additional 1mm washer between driving pulley and the centre bushing. Better acceleration and at least the same top speed, greater than 80mph. The washer is essential to prevent the possibility of the oil sump gasket getting ripped or torn - oil in the transmission area is a no-no.

Hello all,
Thanks again for the help.
Over the weekend I opened up and I can confirm that I placed the sliders incorrectly. I have attached the photo showing how they were in.
Possibility of oil sump gasket freaked me out, so I placed the original rollers back in.
It drives as before now.
However, before we close this topic, I would like to know what could happen if I used these 14G sliders correctly installed?
Can something be damaged?
Would performance change worse or better?

If I order the 13.5 G Dr Pulley sliders, I am not sure precisely where to put the 1mm washer. I do not know where 'the centre bushing' is exactly.
In the attached Piaggio drawing, should it be added to where the #5 washer is, or on the other side of #2?
Can you please help me with the precise location in the drawing where the additional washer should be placed?
Thanks again,
Rick

A lot has been written here about the so-called "fuzzy washers" but this is the wiki page.
Fuzzy Washer Performance Mod Explained

I am very much on the fence about sliders vs. rollers. I have sliders in all three of my scooters and they are fine. The rollers that were in there before were fine too. Probably the sliders' shape makes them more durable than rollers but I had no issue with rollers' durability in the first place. I used the slider weights that somebody else had suggested for my exact scooter, all a bit lighter than the stock rollers, and didn't do any experimentation. Now that my curiosity has been satisfied I don't think I'll go out of my way for sliders going forward.

You don't know what they do, or how to install them, but you are installing the Dr Pulley sliders anyway. Why?
Lighter rollers or sliders will both give you a performance increase. Heavier ones are likely to slow the bike down, because they keep the engine from reaching the powerband while you are accelerating.

The belt is correct and not causing the problem. The HPE belt is 6-7mm shorter than the original GTS belt, and hasn't been causing issues with the oilpan gasket. Some sites are stating that Piaggio discontinued the GTS belt, and is replacing it with the GTS HPE belt for all GTS models. Probably not a bad idea. Here's a company that shows the old part number 82941R as being out of production, and the belt for the HPE as correct for every GTS 250-300 ever made.

https://www.easyparts.com/Transmission-belt-PIAGGIO-Quasar-250-300-4T-4V-E2-E5-2004-2024-p33526655

Try 12 or 12.5 gram rollers. You will have to try very hard to install them incorrectly.

Thank you everyone for your feedback on this. I will leave it with the stock rollers for now and be happy that I successfully changed the belt on it.

I have learned a lot about this and appreciate your input.

This topic can be closed.

Regards,
Rick