agree with the previous comments plus I would be checking the clutch throw, check the adjustment of the clutch arm. You can wind the stop nuts in towards the clutch cover a touch its trade off between pushing the crank against the thrust washers and getting the clutch to disengage. The grey diaphram wont help because of the force needed to push it so the stop nuts will prevent the clutch pressure forcing the crank against the thrust washers
If i adjust the clutch up correctly (from the info provided on here) then i cannot get it into gear. You cant even force it into gear. If i wind the over throw nuts right out (towards the end of the thread) the clutch works fine, just that the engine revs dip a bit.
You have something wrong with the clutch setup, the overthrow nuts should be setup as per the info here, if you wind the nuts off you can load up the crank thrusts. Set the overthrow nuts up and the clearance on the adjustment arm, and then look at the hydraulics to ensure its throwing the clutch fully.












