Small Engines (Lawn Mowers, etc.): Belts, craftsman lt4000, sears

Question
How tight are both drive and mower belts supposed to be when engaged?  Should they both be as tight as my fan belt in my car (1/4" play)? Mine are both very loose and the mower belt falls off sometimes.  The blades don't spin fast either.  I have a Craftsman LT4000 12.5 HP 38" tractor (917.256451).  I can not see where I can adjust the belts?  

Thanks in advance,
Todd

Answer
Todd
They should be tight like in a car with a small amount of free play.
There is a pulley in the picture I am sending you it is # 36. That is called the idler pulley it has springs attached to it to pull it tight against the belts. Check the springs out they may have come off (a common thing with sears) if they are all installed the belt may be stretched out.