kickstart slips when starting

Hi i have a friends scooter at mind it is a vespa 50 in a v100 body with a DR kit and 125 exhaust and carberetta suddenly started when kickstarting it slips as if the clutch was pulled in fitted new polini ali clutch plates and a stronger kickstart cog spring and a new clutch spring and stills slips when kickstarting and now when you try to bump start it slips a bit but will not start anybody help thanks

The clutch cable to tight?