I have been given a Honda HR1950 Lawn Mower with a roller at the rear. The engine works fine. The rotory cutting mechanism works fine, but the roller drive clutch just doesn't engage. I can see the clutch cable linkage moving, and between the engine (gearbox?) and the roller I can see a spindle pivoting when the clutch lever is moved, but without dismantling the whole thing I have no idea how the clutch itself works. Any ideas as to what may have failed?