By: Anonymous: Jeffrey ()  Tuesday, 02 July 2013 @ 06:28 PM ICT (Read 1552 times)  

In today's modern automatic motorbikes, there are weights. Specifically the Honda Spacy, Scoopy, Zoomer X platform they share have weights in their CVT transmissions, what is the weight (in grams I think) and what does heavier or lighter weights do ?

Quicker off the line ? Higher top end ? I mostly have no clue here

By: Flying Squirrel (offline)  Wednesday, 03 July 2013 @ 11:39 AM ICT  

I have not weighed the ones in Zoomer-X etc, so I cannot tell you how many grams. I have some old Click 110 weights under my desk but I cannot remember or find the weight.

It is all to do with the forces generated. If you fit lighter weights, for instance, the engine has to rev a bit higher before the system changes gear. So you can equate this to revving a manual transmission car more before you change gear. If you fit heavier weights the engine "short" shifts and changes into a higher gear sooner. Manufacturers strike a balance between performance and fuel economy. Another thing manufacturers have to do is take into account the weight of the rider. This is why the old PCX had different weights in Asian than it did in the EU/US.

So fitting lighter weights can give you better acceleration because the engine is allowed to make more power as the system moves through the "gears"

Numerically the top speed is limited by the dimensions of the pulleys and by the horsepower the engine develops or is allowed to develop to overcome aerodynamic drag.

That being said it is a balancing act. The rotating forces generated by the weights have to overcome a counter spring in the rear. So it you fit lighter weights the engine has to rev higher to change the ratios. The most common misconception is that lighter weights give less top speed. Depending how light you go as long as you have enough force to completely overcome the force of the counter spring then the top speed will not change. In a few cases, mostly 2-stroke scooters, installing lighter weights will increase top speed.

If you fit very light weights the engine will rev high all the time as the force applied to the system is less. As witnessed by the scooters one sometimes sees, or rather hears, which are ridden up and down sois as it the throttle were a switch. Roar-coast, roar-coast, etc.

Weights are not the only factor. The shape of the ramp along which the weights travel is also important. You can equate this to having gears that are close together as in a sports car or further apart as in a family car. Yet another manufacturer's compromise. Dimensions/diameter of the weights can also be altered.

If the system is designed correctly you can achieve a balance close to ideal where you get better acceleration and hill climbing ability together with a comfortable cruising speed. But increased performance is not free.

Crass commercialism: J.Costa has variators for all the scooters you mention. They are optimized for sporty, everyday riding. Similar to The Honda PCX 125i, Could use a bit more Get-Up-and-Go?


Flying Squirrel

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