How do I change the belt which controls the self propelled mechanism on a V212P4 Snapper 21 inch lawn mower?
Thanks.

Hi,
I gather you mean the one on the left going ot the differential. The bolts to the guide on the differential must be loosened to get access there. The hex shaft must be partially disassembled. I do that with an adjustable wrenck on the hex shaft and a 9/16" wrench or socket to take off the locknut outboard of the left handle bracket. The shaft can be slipped inward, the pulley has a hex area the shaft fits in. The belt can be slipped on the differential pulley, the idler and up to the pulley on the hex shaft which can be slid back the othe direction and reassmbled. Tighten the bolts on the differential guide and you are done.
Peace,
Clarke