how to remove engine pulley on craftsman lawn tractor ?

Hello,

I have a Craftsman LT1000 lawn tractor (16 HP, electric start, 42" cutting deck"). The engine pulley which drives the drive belt for the rear wheels and the cutting deck has broken (the lower part of the top pulley broke off). I am trying to remove the engine pulley, but I cannot get the bolt off from underneath which holds the engine pulley on. The main problem I think is that I cannot find a way to keep the pulley wheel from moving when I try to loosen the bolt. I spoke to someone at Sears technical support and they said the bolt should loosen clockwise since the pulley turns counterclockwise.

I have tried WD40 on the bolt to no avail.

How can I get this engine pulley bolt off?

Thanks.