Do you wish your scooter had smoother, stronger acceleration off the line?

That was the biggest complaint with our 2005 Aprilia Scarabeo 500. Our scooter was one of the last Scarabeo 500s produced with a variator containing six 30-gram roller weights. Later units have the eight-pack roller weight array. Topping 500 pounds ready to ride, this scooter is easily the heaviest among several two-wheel models employing the 460cc Piaggio Master drive train.

The overall initial acceleration was adequate, but more often than not we experienced rough uptake accompanied by stuttering and clanking. Even after some CVT adjustments, the unsettling rattling from the CVT quickly returned.

At right, OEM roller weights from the '05 Scarabeo 500.

Every now and then, the transmission would perform just fine with buttery smooth acceleration. This only served as a reminder that the typically poor start-ups were a real annoyance in need of attention. No wonder Piaggio decided to make some variator changes (although the newer stock design reportedly is not a marked improvement).

Inexpensive performance upgrade

The least-expensive upgrade available was installation of Dr. Pulley sliding roller weights. Wanting to remain close to the original roller weight configuration, we opted for the 28-gram version. A 24-gram roller weight version offered by Dr. Pulley would likely result in slightly higher RPMs and slightly better initial acceleration, but at a cost to both top speed and gas mileage.

Offered by Union Material Co., Ltd. based in Taiwan, Dr. Pulley has marketed its U.S. patented roller weights for a wide variety of scooters and go-karts around the world. The typical roller weight is a simple round design serving a simple purpose – to roll. Dr. Pulley’s long-life nylon design isn’t really a roller. Instead, it slides along by closely fitting to the variator contours for maximum contact and less wear on the ramp plate. So gear ratios vary as the weights slide within the variator rather than rolling around. Of course, Dr. Pulley still calls them roller weights because it would be downright confusing to call them slider weights.

The simple swap out of these weights produces impressive results on the Scarabeo. As claimed, the weights produce stronger initial acceleration. Much of this is probably attributable to the higher RPM at idle. Consequently, the transmission is in a good position to accelerate strongly from the start. Acceleration is consistently smooth and linear. Frankly, a perfect start-up with the OEM rollers was silky smooth, but that sense of perfection was rare and required a super steady feathering of the accelerator. With the Dr. Pulley sliders, you consistently get a very minor vibration from the slide action as you accelerate. When the CVT belt and those sliding rollers drop down, a gentle thud can be felt as you come to a stop. Although this can be heard on the accompanying video, you hardly notice it in real life.

Mileage suffers – but not much

My initial testing in cool weather indicated a noticeable drop off in MPG. To be honest, I was aware that I had been testing the throttle response unusually aggressively. Hey, what a joy it was to open her up without getting frustrated by a rattling CVT. Of course, when you thrash the throttle, your gas mileage will always drop. A fairer test came in warm weather after getting used to the switch for several hundred miles. Overall, I found that the MPG is down by only one or two miles per gallon. In excellent conditions, I often averaged 59 mpg with the OEM rollers. Now, I typically get 57-58 mpg. Frankly, I still probably open the throttle a little quicker than in the past knowing that I won’t get the unpleasant rattling roller feedback I experienced so often in the past.

We have no concerns about putting the Dr. Pulley weights in a stock variator. The product has a good track record, and the reaction has been consistently positive. Just like the consistently strong acceleration with the new weights.

If you haven’t changed a thing on your maxiscooter, this is one of the first modifications you should consider. The change is especially worthwhile if you’re experiencing transmission chatter on initial acceleration. Dr. Pulley is distributed wholesale in the U.S. by MRP-Speed, whose web and retail outlets are likely to carry the sliding roller weights.

- Jim Robins