Originally Posted by maniac57
I'd replace them with allen head bolts for more life and easier tightening.
Ditto, except the you might find the heads of the Allen head cap screws are a little too large to fit the counterbores where the original screws went. In that case you can either grind the heads to a smaller diameter or go back to screws which have the proper size heads.
And yes, they are 6mm X 1.0 thread. One (top right hand side looking at the left side of the engine) is longer than the other two because it was made to mount the kit supplied chain guard.
I'm wondering how you got home if all three screws fell out. The clutch would have been engaged with no way to disengage it. And, if that clutch actuator cover fell off you need to make sure there is still a steel pin protruding from the center of the drive sprocket and the ball bearing that goes in ahead of it.