Modern Vespa

Okay, I am in the middle of no where in PA. I brought both my modded vespas into a shop in Scranton. One was fixed perfectly and now goes 50 instead of 45! I am very happy. However, the other went 42 and now goes 25. It needed a new belt and has a malossi variator (and belt). They put a vespa belt on and now it revs high, but doesn't have the speed. I am guessing this is a belt issue. Does anyone have any ideas? I am not a happy customer.

I believe the malossi belt and stock belt are different lengths. This is probably your problem! Probably ought to order a new malossi belt and swap it on there

If the belts are of different lengths then they are not the correct belts.

It sounds like the variator is not working properly. It will sometimes just need to be cleaned up and reassembled. If it's been this way since you picked it up it could have been that it just wasn't given a thorough enogh test ride. If it's gradually happened then you have some other problem that is keeping the belt from traveling it's normal route.

I've only run stock myself, I just thought I read it on another thread here... something about the performance belts having slightly more (or less?) slack to go with the performance variator

Yes, this is true. If you have a larger pulley there are special belts to accomodate. But that's just for the sets like the MHR. But I think that was only on the minarelli engines. They genrally have a smaller rear pulley. The MHR overange kit just makes it about as large as a piaggio rear pulley.

And I think they all may come a few mm plus or minus in length. But if it's so big there's slack it's probably the wrong belt. I was thinking my ET2 belt was too short. It doesn't ride to the fullest diameter on the rear pulley. I was thinking with a slightly longer belt I could afford an upgear given the lower starting ratio if I could take advantage of that extra rear pulley diamter.