Finally had a chance to do some testing of DR Pulley sliders. I would like to point out that I have many years of tuning and racing high performance motorcycles. When I make any change I try to test the change to make sure if and how much that change effects performance. One thing I learned long ago is that the "butt crack" dyno is the least accurate method of measuring performance. For scooter testing I have a "secret" test site I use. Very little traffic, up hill, about 120 yards long. I make 8 full power runs between paint marks on the road, timing each with a stop watch. In addition, I have a small electronic tach with memory. After each run I record time and max RPM's reached. Throw out the best and worst runs and average the remaining 6. Admittedly not very high tech but for the money it's a pretty good method.
To start the testing I first did a baseline. My bike, '12 Kymco GTi 300 with 9K miles, completely stock including top case and stock rollers lightened to 13.2 gr. by drilling them out to 3/8 inch. My time average was 8.42 seconds with RPM peak of 6190. With stock 15.5 gr. rollers I have recorded 8.66 time back when the bike only had about 1000 miles on it.
Next I installed 15 gr. sliders. Normally I only make one change at a time but at this time I did check the air filter and gave it a good cleaning. Not sure how much the cleaning effected the test but am sure it was very little. Time dropped to 8.04 sec. @ 6380 RPM's. This is a very dramatic improvement, enough to convince me to go with DR Slider in any scooter I own. Top speed, using GPS and a two way average, was 84 MPH, exactly the same as before the change.
With sliders lightened to 14.2 gr. the numbers improved to 7.87 @ 6710 RPM.
Finally lightened to 13.6 gr. numbers were 7.68 @ 6865 RPM.
I've not tested top speed but have no reason to think it has changed. Peak torque for this motor is at 6500 RPM and peak HP at 7750. I think you get your best acceleration over a given distance if you can get the RPM's up near the peak HP figure and above the peak torque value. On the GPS top speed test I reached 7888 RPM. At that RPM the bike is past the power peak where power drops off fairly quickly. Meaning that it simply will not go any faster unless something is done to increase HP and the RPM of power peak. It is possible that a slight change in gearing might yield a couple MPH but changing gearing is not an easy task. Also, taller gearing, if possible, would come at a cost in off line performance.
For anyone interested, the drill to use for various weight sliders is 11/32 = 14.7 gr., 23/64 = 14.2 gr., and 3/8 = 13.6 gr. Hope you find this useful. My conclusion, I'll keep the 13.6 gr. sliders but will order new 15 gr. ones to install if I undertake a long trip.
