Why Use An Over-Running Clutch On Your Yanmar Tractor

All Yanmar grey market tractors all need to have an overrunning clutch when using a high energy implement like a brush mower. 

The reason you need an overrunning clutch is that none of the YM series Yanmar tractors have a "live PTO". The transmission is directly connected to the PTO. If you depress the clutch you will disconnect the PTO and the transmission from the engine but the PTO and transmission will still be linked together.  This means that if you spin up a big mower on your PTO and the transmission is in gear, depressing the clutch will not stop you from moving. The momentum of the mower will continue to move the tractor. It will continue to move until the mower loses momentum and comes to a stop or you shift the PTO or transmission into neutral (which can be difficult if they are under a load). 

An over-running clutch acts as a ratchet. It allows the engine to turn the PTO but does not allow a PTO implement to feed that power back to the transmission. Exactly like your ratchet wrench. 

OverRunning clutches either slide on to the tractor's PTO using a quick coupler just like your mower shaft or they are held on with a roll pin which requires a little extra install time.

Pro Tip: You might need to trim your mower's PTO shaft (using a chop saw or hacksaw) so that the shaft does not bind when raising or lowering the PTO. There are lots of videos on YouTube showing how to do this. 

Overrunning clutches are typically only needed with high momentum implements. If you depress the clutch and the implement stops quickly (like a tiller) then an over-running clutch might not help much. 

Buy Your Over-Running Clutch HERE

Is an over-running clutch a slip clutch? No. a slip clutch will 'slip' if a mower hits a big stump or something gets bound up in the mower like a roll of fence wire (oops). These two types of clutches are for completely different purposes.