how to repair a steering problem on riding lawnmower?

Sounds like either those flimsy little plastic bushings that fit over your steering rod where it fits through the frame holes are worn and need to be replaced or the two that fit on top and bottom of the main gear where it fits through the housing that connects it to the teeth on the end of the steering rod. However, this is my thought because you mentioned the 'popping' sound. It could also very well be that the bar connecting the main steering gear the front left wheel spindle is held in place by a sort of ball-joint set up and it has wallered out due to tight turning or sharp turning through rough terrain. Look under the mower and follow the rod from the steering wheel to the bottom where the teeth are welded and meet the main gear. If you can grab the gear or steering rod and they wobble without much effort it's probably those plastic split bushings, but if not then follow the rod connected to the main gear to the front left tire spindle assembly checking both ends for a snug fit. If you can freely move the ball joint or it falls out the best 'quick fix' for this is to push it up in the hole and hold it snug with some rubber bands and then apply as much duct tape as possible without affecting steering. This will hold for a little while depending on how much and what you're cutting, but it's better than having to buy the replacement gear, spindle assembly, and draglink assembly that has an actual stud and nut connection rather than the ball joint.
Hope this helps.

bigomoe
June 2010