I recently purchased an OS 21tm, new clutch bell & heavy duty slipper. After fitting these parts I proceeded to break in. Firstly the engine would only start with the air filter removed, replacing it while the engine is running would cause the engine to stop. Secondly, when applying throttle the engine, revs would increase but the revo wouldn't move. Does anyone know why this is? Is there a incorrect way of mounting the clutch shoes on the flywheel? Any help would be appreciated, I'm keen as to see how this engine performs in my revo.