I have a snapper 12.5hp 28inch cut rear engine riding mower. When i start the mower and put it in a forward gear and let out on the clutch/brake peddle, the mower tries to shut down unless i push the peddle back down. But when i put it into reverse it moves fine. I have noticed that when going from the reverse gear to a forward gear it feels like the clutch is not ingaging correctly.
Sounds like the belt is grabbing. When was it changed last? Grab the shift lever while you are letting up on the clutch, do you feel the tranie engaging in a gear?