You might all of the sudden hear a knocking noise coming from the front of the right case cover. Sometimes you can also feel a slight knock when laying your hand on the front of the cover. Upon inspection, you might find that the 3 bolts holding the starter clutch together are loose and have backed off enough to make contact with the inside of the cover. If so, remove the bolts one at a time, clean and inspect them. Clean the threads in the starter clutch housing and re-install the bolts with a drop of RED Loctite and torque to 22 ft.lbs. If the bolts are really banged up, they should be replaced.

Another noise associated with the starter clutch when the engine is running is a grinding or rattling noise that sounds like it is coming from the inside of the right engine cover. This can often be caused by the rollers in the starter clutch free-wheeling over a rough center gear roller engagement surface when the engine is running. Before disassembling the starter clutch, you can spin the center gear in the starter clutch housing to feel and hear the noise. If you suspect this is causing the noise, inspect and rebuild the starter clutch as needed.