Engine will sputter and start to die after 10 to 15 minutes mowing, but will not completely stall if I quickly turn off blades and use full choke (clock display goes blank as this happens). After a couple of minutes, the display returns and I can remove the choke to smooth it out and restart the blades. This continues to happen with increasing frequency unless I disconnect the regulator/rectifier, which prevents further problems (replacing the regulator/rectifier did not solve the problem). Twice the engine refused to restart after a normal shut-down (with the key). Display remained blank for several minutes until it suddenly reappeared and engine could be restarted normally. Two snapper dealers have been unable or unwilling to solve the problem. So far, I have replaced the regulator/rectifier and the seat safety switch. I now suspect either the safety switch that keeps the engine from starting when the PTO is engaged, or the safety switch that prevents the mover from backing up when the blades are engaged (unless a dash lever is activated). I need wiring diagrams and operation details of these two safety devices before I can continue my search for an answer. Any help in diagnosing this problem will be appreciated.