So I have a 1980 Garelli that usually runs well, but a lot of the time when I have the clutch engaged and I pedal to start the bike it doesn't engage the motor at all and just spins the back wheel as if I wasn't pulling in the clutch at all. If I slowly crank it, it will catch and the motor will turn over but its not enough to get the bike started. Any rapid pedaling will cause it to slip. Any suggestions of places I should start to look for problems? Thanks.
P.S Here is a video of a guy who is having the same problem as me.