Small Engines (Lawn Mowers, etc.): Blades wont engage on riding mower, craftsman riding mower, tension spring

Question
I have a Craftsman riding mower.  When I start my mower and engage the blades, they will not run.  I have replaced the belts and still have the same problem.  The strange part is sometimes I can start the mower and the blades will start running instantly, even though they have not been "offically" engaged.  It's like they have a mind of their own.  Can you please help?

Thanks!

Answer
It sounds as though you have an issue with the linkage(s) for the blades.  This coud be a broken tension spring  or something bent that is not tensioning the belt correctly.  It could be an adjustment also causing the blade brakes to not disengage.  You are going to have to go over the assembly thoroughly.  If you cannot find the problem, make sure to take it into a good shop and don't continue to use it not knowing whether the blades will turn or not.  Hope this helps.