gilera stalker clutch problem

hi im new to this site and dont know much about scooters but i know the basics.
anyway i have just purchased a 54 reg gilera stalker 50cc as spares/repairs and the problems were the piston was f*#ked and the clutch wont engauge properly. i have sorted the piston got a new 1 the replaced all gaskets (head cylinder and exhaust) aqnd the bike is now a runner apart from the clutch i only spins the wheel at about 4-5mph i have checked the rollers (like new) clutch pads are hardly worn and not glazed so could any1 help me out on what the problem could be??? i can give more details if needed
thanks in advance
chris

sounds like a worn belt slipping from your description, or it could be that the previous owner may have fitted stiffer clutch springs

i cant work it out ive have the side case off and the clutch bell spins faster wen i rev it but the wheel only move super slow the belt/rollers/clutch pads are all like new hardly worn so im stuck on wot to do is there anything else imn not checking????

check the clutch springs

what weight are the rollers, if there too heavy this will kill the bikes speed

So I have problem. Where I Am reving my bike half throttle before moves. Any idear guys

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