I've got a Lawnboy 10685 sensa-speed, insight lawn mower. I've never had a problem with it until yesterday. I suspect that the inductive, safety device for the rear bag/mulch plug is not allowing the mower to start. It ran fine then suddenly stopped as if I had let go of the blade control bar. The gas is good and the filter is new. Does the mulch plug bar have to make solid contact both top and bottom to complete the saftey circuit? I've tried wiggling it, resetting it and even putting the rear bag on instead but no luck.
How can I troubleshoot?

 

OK it's getting stranger. I can start the mower if it has sat for over an hour. One pull without priming it fires right up. This time I let it idle for several minutes, gently revving the throttle by hand. All is good until I start cuting a swath of grass. It's not thick or deep grass either. On a slightly downward slope the engine quits. It doesn't sputter like it's running out of gas, it just quits and will not restart.

 

May be a problem with the CDI module or with the control cable that operates the engine kill switch.

How old is your unit, this could possibly be covered by warranty.

 

I believe the mower is between 2 and 3 three years old.
Can the engine kill lever be adjusted? I've looked at both ends of the cable and it is a set length with crimped "z" shaped tongs on both ends.

 

It does not appear to be adjustable, you may want to check to see if your getting spark when the mower does not start. You can unplug the switch from the bagger/mulcher switch to isolate it to see if it's the problem.