Modern Vespa

I decided to give my MP3 400 an early maintenance service at 9,000 miles. I had a couple of parts replaced today: Rear tire, front brake pads, belt, and replaced the old rollers with the Dr. Pulley slider weights [16gm]. At 9,000 miles, I was surprised to see the original belt was still new with no sign of cracks anywhere, but I replaced it with a new one anyway. My main reason for this posting is to report the performance of the Dr. Pulley sliders. I must say, the new sliders definitely gave my scoot the extra boost during the initial take off. I love it! I am all set for the winter.

That old rear tyre was completely shagged! I bet the new one feels better.

A visual inspection is not sufficient to determine if a belt should be replaced.

If you measure the width of the old belt it will be narrower than the new one from wear against the pulleys. This has the same effect as the belt being long because it will sit lower in the pulleys. Some have worn to a point that there was some stuttering at slow speed. When the variator is full open a worn belt is sitting at the bottom of the pulley and not wide enough to have proper grip until the rpm increases closing up the variator. The belts still looked good but a new belt eliminated the stuttering.

At the 6200 mile service on my MP3 400 my belt had worn over 90% from the new belt width to the minimum in the owners manual. It looked great but the difference in width was visible put beside a new belt. My belt was not worn to the point of performance issues, but I could tell a difference in the ride from being in a higher gear with the full width belt.

I have to say I've never found any sensibly measurable difference in width during the life of my belts. The Honda belts as used in X9 250's certainly suffered from this, but the Piaggio ones appear (to me) not to.

[If you measure the width of the old belt it will be narrower than the new one from wear against the pulleys]
Fuzzy - I still have my old belt and will save it to compare it to the new one next time I need to replace the belt again. Learning something new every day. I really appreciate your feedback.
By the way, do the rollers worn out in thickness like the brake pads if I were to compare them to the new ones you know?

Rollers just get flats on them.

You can measure the old belt with a caliper and compare to the specification in the manual to determine how far gone it is.

the ones that were removed from luthorhuss's after 9k miles had no flat spots they were a little worn looking. not even noticable smaller diameter wise. even the inside brass bushing was ok.

[the ones that were removed from luthorhuss's after 9k miles had no flat spots they were a little worn looking. not even noticable smaller diameter wise. even the inside brass bushing was ok]
So what factor determines whether it's time to replace the rollers besides following Piaggio's recommended service schedules? If the worn is not too noticeable, how do our mechanics determine that they need to be replaced or not?

you could mic them but for the cost of them why would you not just replace when they already have everything apart. labor rates being what they are and such. If your a DIYer then you could check and monitor them every 2k miles just for gee whizzes.