I have a craftsman riding lawnmower and the blade engagement is not starting the blades when i lift it. It feels loose when i lift it.

Try checking your seat safety switch by TEMPERARLY bypassing it..try the blades if ok..your seat switch needs replaced..good luck..

Things you need to check, loose blades, blades out off balance, bad belt or loose belt, bearings in the blade mandrels worn.

did a cotter pin fall off

just replaced some pulleys on my craftsman 42 inch cut and now the blades are ingages all the time, but it will start

You haven't specified the model number, but pretty much all riding mowers use a plunger-type electrical switch to engage the mower. If it's stuck in the 'lifted' position (mower engaged) then it has broken internally. You must replace it. In doing that, the wires need to be placed back on the correct terminals, so take a picture of the wires (showing their colors) before you disconnect them from the switch. Take the broken switch to a lawnmower shop to find a replacement. Shouldn't be more than $10 - $20. Good luck! Please rate my solution if you found it helpful.

My craftsman lawn mower will not engage the blades

get down and gun your fingers in the slot that the belt rides in, soulds like you may have a small rock or piece of wood lodged in the v part of one of the pulleys. I bet thats it Jim

if you mean that when you let off the clutch pedal and/or engage the blades, the engine dies, lift the seat and make sure the connector is firmly plugged into the switch attached to the seat.

maybe the safty switch under seat might be starting to go out if that switch doesn't work the blades wont come on at all for safety

You deffinately have a loose wire or connection coming off that switch,youll have to investigate to find out where it is.