Small Engines (Lawn Mowers, etc.): riding mower wont engage, riding lawnmower, safety switch


Question
i have an old riding lawnmower. a craftsman. it has sat for a while, but i managed to get the engine to start and run.  now that the engine is running i thought all i'd have to do is select a gear (R,LH) and go.
with the brake pedal fully engaged and putting the mower into gear (when i do with engine off at this point I am nno longer able to push mower so i think it must be in gear)if i depress the  plunger at the  top of the vertical lever on the right side of theengine, i can feel the brake being pushed back and then the mower quits.
i have removed the panels across the top of the deck and seat and can see the gearbox. there is also a switch that engages when the blade pulleys are engaged, but i cant tell what could be wrong.  should i just change out all the pulleys? is it a pulley problem?  is there a safety switch i should look for?
i'd like to get it running as i got it free from my neighbor and really dont want to go buy one.
many thanks,
Tony

Answer
Hi Tony,

I think it might be a safety switch.  They are usually located under the seat and on the blade engagement lever as you saw.  Test the switches by temporarily bypassing them, using a test light or meter.

Let me know what you find.
Michael