Have 21 HP 46 in Craftsman riding mower 917 288520. Had to replace bent mower blade. Tipped up to replace blades and now mower deck won't engage. Starts and runs fine but blades won't engage. Belt looks in place. Any suggestions?

You better check that belt closer that it isn't snapped or off anyplace. Its mechanically engaged... Last time I bent a blade I snapped a belt too.

I've got a 20 hp 42" deck...

Hi,
Also, check to see that the cable is still connected on the deck. Link to the manual is below(just select the Download link.)http://www.searspartsdirect.com/partsdirect/part-model/Craftsman-Parts/Riding-mower-tractor-Parts/user-manuals/manual-downloads/Model-917288520/0247/1509200?modelNumber=917288520&diagramPageId=00004&documentId=1108179P
Peace,
Clarke