If your talking about a auto scooter clutch then that's how they work, there has to be a certain amount of slip before it fully engages, have you got heavy springs in it?
funnily enough..... To answer the original question they are both slipping really. At the start. The rate of slip of the clutch varies according to the stiffness of the springs - but if it's a centrifugal clutch with the springs working in extension (ie 99 percent of clutches out there) then above a certain RPM it can't slip at all. This generally occurs around 5 mph standard springs - and maybe 15 mph for really stiff springs. After this, there is just too much centrifugal force for them to slip. The wings might as well be welded to the bell. Now belt slip is different - and belts are always slipping more or less. This is dependent on the weight of the rollers and also the width of the gap in the variator between the running surfaces relative to the width of the belt, and the state of the belt itself. If you add a washer (like in the video) then the variator lets the belt slip more on take off than it otherwise would. I think this is not exactly because the gap is bigger to start (the variator just moves out to pinch the belt anyway) but in fact it's because the rollers are further up their little ramps when they do start to pinch the belt and force it up higher on the running surface. This effectively reduces the mechanical advantage the rollers have over the spring at the back variator - and so the engine revs higher - for a given roller weight. Until everything is going very fast indeed. Whatever the reason - after a while, most set ups benefit from a 0.4 mm washer when the belt is good and worn. Counter-intuitively - the belts grip better the older they get. Put a brand new belt on a scoot and you may find you can remove your washer because the new belt is slipping more. Variators and clutches are a balancing act. You sort of need to feel where the problem is and modify the system to get what you want. And it's no good someone saying 'use these springs' or 'use 5 gram rollers' because every scooter is different, has a more or less worn belt, more or less torque according to pipe/carb/cylinder spec etc. Even different variators behave wildly differently, according to the change in the profile of the roller ramps, angle of the running surface etc. The variator in the vid is a Doppler SBR2 and it uses about 4 grammes less total roller weight to work compared with the Malossi Overrange variator that I also have with the same engine. There are other differences too - especially at mid range and high speed. The Malossi is a 'track' variator - it pulls really well from the start to the middle - whereas the Doppler was clearly designed for high speed cruising. They are completely different beasts. This is just to illustrate the point that variator geometry is not all the same. Basically, if you've done everything you can to stiffen the clutch but the take off is still crap, experiment with some top perf washers. They come in various thicknesses, and they are the exact same diameter as the slider in the variator. Start small. If you have a standard variator then you can actually reduce top speed if you use more than like a 0.4 mm washer. The variator travel is limited and if the gap is too wide, the belt will ride up lower on the variator. And of course, a transmission that loads the engine sooner (ie not much clutch slip and heavy rollers - in other words all standard scooters) will want more juice at the start of the throttle opening, so don't forget to have a fiddle with the richness/airscrew to get the best pull of the blocks. Good luck !
Thanks Guys for your information I changed the belt in my mates Aerox 100 and it made all the difference. The belt was 4mm too narrow Thanks again Gaz
