Bolen 15 hp engine runs fine. When in gear I can get it to run in 4th, maybe 5 sometimees, 1-2-3 do not work, sometimes have to jurk it forward to engage. Seems like a belt is lose. How easy is it to change it myself. Somewhat handy and can follow directions (not what my wife says). Once going runs fine but inclines gets testy, have to jurk forward to keep going. If I hit the brakes it take a while , again jurking forward, to get going.

Hi,
Need some model numbers here; Bolens has been its own company, part of Gardenway and now part of MTD. They have been around longer than most with huge differences depending upon age.
Peace,
Clarke

Model 13am662f163

Hi,
I will post a couple of images from the IPL. The top image has the speed control linkage and adjustment #33 and #62. They attaché to the pedal and allow the variable speed pulley bracket to rotate. Also, note springs #58 and #59 which balance the action of the bracket. First guess ia that one of the springs broke or fell off. They attach to opposite sides of the bracket and to notches in the rear frame.
In the second parts #21 and #28 are the neutral adjustment, and the bracket is #4. These come from the IPL which is available for your model online, #769-00642A. It can be found by typing in your model number in the appropriate line and a 1 in the serail number line at:
PDF Manual Web Archive
Peace,
Clarke