Honda Harmony 1011 - Cranks but wont start

Hi

I have an old Honda Harmony 1011 riding lawn mover. One day while it was idling I heard a reasonably loud snapping sound, and then some smoke from the engine area. I turned off the machine and now it wont start again. I have opened up the machine and I could not locate any broken parts. It cranks just fine, the starter motor engages with the fly wheel, but still the engine wont start. I have a new spark plug and there is clean gas in the carburetaor float chamber. Any clues? I was wondering if its the ignition coil, but I would like some expert opinions before I buy one. I was also wondering if this is a electrical issue? I know that the engine will not even crank if its not in neutral or the foot brakes are not on, or the cutter is engaged. Is there any other electrical break that could prevent the engine from starting? There are rats in my shed so they could have chewed through some cables too. I replace the stop switch cable that attaches to the ignition coil, but no difference. Infact even with the stop switch completely disconnected the engine cranks but will not start.

Any clues?

Thanks
Aspi

That's a fine old mower.
Take the spark plug, poke a ticks, screwdriver etc down the plug hole apply light pressure to the top of the piston while you rotate the engine by hand.
You should feel the piston rise smoothly then drop smoothly, be careful not to snag whatever you are using as it gets near the plug hole.

if that is good then put you thumb hard over the plug hole and crank the engine, it should be hard to hold back the pressure.
While you are doing this check for a spark at the plug , but I doubt you will get this far as I feel you are looking at a broken rod or cam.

Thanks lawnking. I poked a screwdriver down the plug hole. At first it seemed blocked, but then I was able to push down on the piston, and now the piston wont come up again. If I push the piston all the way down and then try to rotate the fly wheel by hand, I can feel it being obstructed. But jiggle the flywheel a bit and the piston will move up just a little (maybe 1 cm). It never comes back all the way up. I think that its time to give this away.

Thank you

You have a broken con rod.

SO it is out with the engine and pull it apart.
What you see when you pull it apart will determine if the engine can be repaired.
You then need to decide if you want to.

Your camera has now become your best friend.
Take close ups of everything, all of the wire plugs and carb linkages.

Photo the inside of the engine, the inside of the bore , post them for analysis.