engine dies when blades try to engage

Check that your throttle is at the correct setting {IE not on choke or idle setting) insure your transmission is in acceptable gear, also note that riding mowers have a seat safety kill switch- deadman switch, so check that its functional, They also may have a kill switch for reverse. Some have an ignition switch with 2 run separate run positions. 1. for blades engagement while reversing and 1 for safety- engine kill while reversing with blades engaged.