Most of today's tractor mounted rotary lawn mowers are driven by a common V-Belt drive. Here are a few tips to follow when servicing your belt drives.
When replacing A V-belt never pry the belt into the groove with a screw driver or pry bar. this will only damage the cords and cause premature belt failure. Always loosen tensioning sheaves and install the belt and retention.
Inspect the grooves of the sheaves. A V-belt drives off the sides of the V, if the bottom of the groove is polished that is sign the sheave is worn and belt is driving off the bottom. If the belt is running on the bottom of the groove it will necessary to increase tension to reduce slippage. When the tension is increased you run the risk of damaging the belt from over tensioning.
Always insure proper alignment between sheaves. Misaligned sheaves will cause excessive side wall wear of the belt and can in extreme cases cause the belt to roll in the groove or jump off. Use a straight edge or string to check alignment of sheaves. All sheaves should be within 1/16" for every 12" of sheave centers.
Never use so-called "belt dressings" on any V-belt. Most are made from petroleum derivatives and can have a destructive effect on the rubber compounds of the belt. If the belt is slipping check for proper tension or worn grooves.
In abrasive conditions such as sand always keep all belt shield in place to prevent abrasives from getting into the belt drive. Abrasive material can accelerate the wear of both the belt and sheaves.