DLH 16X13 ROUND ROLLER WEIGHTS FOR 50CC 4-STROKE QMB139 ENGINES. GEAR RATIO IS CHANGED BY THE UP-AND-DOWN ROLLING MOVEMENT OF THE ROLLER WEIGHTS IN THE RAMP OF THE MOVEABLE DRIVE PULLEY (MDF). THIS UNIQUE ROLLING MOVEMENT PROVIDES EXCLUSIVE ADVANTAGES TO INCREASE CVT PERFORMANCE. WE RECOMMEND STARTING PERFORMANCE UPGRADES BY CHANGING THE VARIATOR ROLLER WEIGHTS FIRST. HEAVIER ROLLER WEIGHTS= A SLOWER TAKE OFF SPEED WITH LESS ACCELERATION AND A HIGHER TOP SPEED. LIGHTER ROLLER WEIGHTS = A FASTER TAKE OFF SPEED WITH MORE ACCELERATION AND LOWER TOP SPEED