Are you using the Robins subaru on friction drive? or chain drive?
Subaru clutches are almost bullet proof, I have 2 Robin subaru engines with a lot of miles on them and have absolutely no problem at all.
Are you trying to take off from a standing start? If you are you'll tear up the clutch.
You have to pedal assist and get up a little speed before you hit the throttle.
The chain drive will require a transmission such as Stanton's.
buzzard