Do you control mower speed by tightening or relasing a bail on the handle? If so it is likely as simple as adjusting the cable sheath to tighten belt tension. If you have ever adjusted bicycle handbrake or shifter cables the concept is the same.

I kind of looked at that when I had the belt cover off and what I did was look at what the cable was connected to. It was a smaller pulley that when the handle was engaged, it would lift the pulley to engage the belt/wheels. What I noticed was that when the handle was pulled, the pulley was at its up most position. I tried with a screwdriver to lift further the pulley and it did not go any higher. Either way I will see if I can tighten it to increase belt tension. Thanks for prompt response.

The adjustment should be as simple as moving the cable sheath.

I did just this, adjusted the cable and only see the wheels engage quicker but same speed. Any other parts to look at? Thanks