Small Engines (Lawn Mowers, etc.): How ro adjust drive belt for deck, sears craftsman lawn tractor, craftsman lawn tractor

Question
I have a Sears Craftsman lawn tractor 19HP 42 inch model 717.270771. The blades are not rotating fast enough to cut the grass. the deck belt seems ok and the spring load tensioners are fine. There must be another belt that drives the deck pulley.  How do you adjust it. Can you refer me to a sketch or picture of that drive assembley. Thanks.

Answer
Is the model number a 917.270771?  If your model number is 917.270771 then you can find the manual at the address below.

http://www.searspartsdirect.com/partsdirect/part-model/Craftsman-Parts/Riding-mo

Eric