John deere d140 lawn mower shoots of when i ingage the blades

Try the following test. For safety purposes remove spark plugs. Now with engine off and key in run position turn PTO on. You should hear the clutch engage (clunk). Grab both sides of the clutch pulley and try to rotate the pulley. If the clutch is properly engaged you will not be able to rotate the clutch pulley without turning the engine.

does it have electric PTO ? if it does then you should be able to hear it click with ignition on and engaging pto switch if it does not then you have to look for a bad safety switch located under seat and brake pedal try unplugging pto clutch and putting 12 volts dc to one wire and grounding the other wire if it clicks its ok if it does not then safety switches are the probable cause witch is causing an open circuit.

Turn off the blades

check and see how much fluid in trans mission and change hydrostatic transmission filter

The drive belt may be broken, or it may have slipped off a pulley.

I believe this one has an electric clutch. Check to see that the switch is operating properly, that the wiring is good to the clutch, and that the clutch is good. Use a volt meter to check that there is voltage to the clutch when the switch is operated.

it sounds like the safety switch under seat is bad

not trying to insult your intelligence, but did you make sure the belts were installed properly.it does happen to the best of us..good luck

your electric pto clutch switch is bad replace it