Modern Vespa

Scooterwest has a performance belt/service kit for the liberty 150 and the vespa 150s that use a 12.5g roller instead of the stock 14g rollers.

Performance Belt Transmission Kit

The description talks about some big performance gains with the lighter rollers. The logic makes sense, but wondered if anyone has any experience with the lighter rollers on either a liberty or vespa 150?

Also, I hear that the lighter rollers can reduce your top speed. I'd be interested if anyone know to what extent. I'm out in the country with long straight aways, so might avoid this if my top speed is too impacted. Thanks for sharing any insights!

I put Malossi 12.5g rollers in my 2019 Primavera when it had only 1200 miles on it. I noticed a slight improvement in acceleration but I wouldn't describe it as a "big" performance gain. It did not affect the top speed.

You have to go ridiculously light to affect top speed. As long as the variator gets to 'top gear' you'll maintain top speed.

So, yeah, it sounds like it won't affect top speed. And maybe it's marginal acceleration help. At 2.5g difference, it's not much. I guess I'll just do it and not set my expectations too high.

Are your stock rollers due for a change? I like DP Sliders for a couple of reasons. They last forever, and they give a good boost to low/mid range performance. Stock weight on my Buddy 125 is 10.7 grams. With 9 gram sliders, there is no loss in top speed and getting from 0 to 40 is a blast. Much smoother off the line, much better acceleration. I have 20,000 miles on this set, and they still look great. It's the lighter weight, unique shape and slickery material they are made from that works so well. It takes a while for them to bed into the variator. Performance usually improves slightly as this happens.
2.5 grams is a pretty significant change in weight.

Well, maybe it'll have a bigger performance boost than I thought. I've heard of those sliders before but don't know much about them. They do have a different kind of shape, which must impact the performance (besides just weight). I'll take a look at them, thanks!

doing a some reading, I think these dr pulley's look like a great option. For the liberty 150, I can see they are 19x17mm and they're offered in 3 weights (8.5, 9.0, and 9.5).

Based on some reviews, the small weight difference has a big impact. Kinda looks like 9.0g would give me the biggest acceleration boost while minimizing the top speed hit. But even 9.5g is a lot less than the stock 14g. I'm guessing the different shape of them is why the gram sizes are different.

Are you sure of those weights for the LT150 rollers? The LX150 has a stock weight of 10g (19x17) and 8.3g (some rollers I acquired years ago) is perfect in our LX with the Malossi 190 kit with an upjet in the carb.

If you're in a position to do so, I would pull the stock rollers and weigh them before ordering. More than once I blindly relied on a printed chart only to find out the weight in mine was not the same.

Yeah, according to scooterwest.

"19x17mm and 15.4 grams. The 3-valve 150cc motor runs a lot better and faster with these MALOSSI WEIGHTS IN A 12.5 GRAM"

That's what got me looking at the lower 12.5 to start

I guess the roller weights are matched with the contra-spring and final gearing to give respectable standard performance with the larger diameter wheels of the Liberty.