My Poulin Riding Mower

You report a sudden change in peroformance after a loud noise. You suspect belts were involved and you saw smoke. Now the electricals don't work and the motor will now turn over.

As recommended by post #2, check the mower plate, but also look at the shaft where it goes "up" through the deck.

You might have snagged the electrical wiring, some rope or even a drive belt around the driveshaft and that has tightened and has stalled the mower.

Remember ALWAYS sparkplug unplugged (or even removed) before attempting to spin the plate by hand to see if it's tight.

Sounds like you may have been low on oil and overheated the mower which caused a dropped valve that then caused a sheared flywheel key when the engine was stopping from high speed.

One addition to the above. The lights on riding lawn mowers typically are linked to the generator not the battery. Therefore they will not light unless the mower is running.

Guest,

Thinking it through...at the center of all your described symptoms--ignition circuit, headlight circuit, and starter circuit--is the multi-pole, single/momentary-throw rotary starter switch. So that is your starting point for solving the problem (and quite likely the problem as well).

Explaining further:

• Riding mower headlights (switches) are not fed from battery but elsewhere, most likely the starter circuit. By design, starter switch must be at ON to enable headlight switch-on...to prevent accidental discharge and ensure optimum voltage for engine starting.
• As you were mowing, an interrupt occurred in the power to the starter switch ... it could have been a switch ground fault (or ignition module or other ground interrupt) which would have immediately killed the engine...same as if you had turned of the switch manually to ground the armature and kill the engine.
• The clunk was probably only a reaction in the engine or mower blades...not likely significant OR..
• The clunk (most likely) came from the electric PTO (mower drive) clutch...if mower-engage is started with a switch and not by a manual engage lever.
• The puff of smoke...same thing as blade and engine continued turning with no spark to burn the fuel...or blow back from intake valve.... Again, probably not something to worry about.

So work the problem as an electrical problem. Tag, disconnect and remove that starter switch (you can test in place if space permits); then check continuity for all switch make-break circuits in all switch positions. If you don't have reference to your mower's switch schematic (in your manual or part manual drawings), make your own as you check switch make-break continuity-discontinuity. Also check for shorts (incorrect continuity between what should be isolated make circuits in the switch. Possible you might also see burn tracking during visual inspection. ) This (fixing or replacing of that switch) should solve your problem. But if the switch tests good...

Then you will want to trace out and assure continuity in (first) battery-switch circuit (including ground), then starter, then ignition to find the interrupt or ground fault.

Good luck with it...and also, what engine in the rider?

Oh yes! Another electical possibility would be with a failed safety interlock switch:

• Dead man switch in seat (kills engine if operator leaves or leans too far out on seat)
• Blade clutch switch lockout (prevent engine from being started with mower blade drive clutch engaged)

You can isolate (disconnect leads from) and manually operate any of these switches while checking make-break with ohmeter.