Honda GB40 Outboard Motor Manual., Page 19Get this manual
1Reassembly Assemble the clutch lever (rear) in the reverse order of disassembly
JDescription of Tension Pulley
The purpose of the tension pulley is remove the slack in the belt and maintain the belt in constant tension when the clutch is engagedSincethe pulley itself rotates, ball bearing is used for minimizing friction(Fig25)