The 4th bearing will protect the crank from breakage. The J/S will allow you to keep the extra heat from the clutch going back into the engine, and also running like a 2:1 primary ratio will lower the clutch engagement which will keep the clutch cooler and make it last longer. Also if your engine has a 1'' crank journal you get the belt driver for a 1'' and then you can run the regular 3/4'' clutch on the j/s. Yes it is extra expense to start but the idea is to save you money in the long run and make your equipment more reliable. Burris makes a nice 4 stroke j/s mount that I would look into.jmo