Do those mowers have a Low Oil Pressure Switch? Put a 'Check Oil First' sticker on the engine..
There should be some electronics that won't allow starting unless you do.. GREAT IDEA
Sounds like you may have serious internal Damage. If you hear a knocking sound when you try to start it, the engine is likely toast. Powerwash it externally and see if there is a hole in the block, or where it was leaking.
Add some oil before trying.
You should NOT be using Teflon Tape for NG or Propane joints. Use the white paste. Proper shutdown, leaving Tank empty, no Fuel in Carb will result in quick Starts.
I never use StaBil etc and Premium Fuel is no longer available in Canada thanks to Woke Lieberals. The cool down after shutting off Fuel Supply is also beneficial I believe. First Pull!
Absolutely Totally Correct Procedure. I only fill the tank 1/2 full but the key is to use the Fuel Shut Off valve every time once you get it running correctly.
Do the Simple thiings first. You were correct in dumping the Crankcase oil. Some residual oilmix may remain in the Intake or Exhaust manifold. Install a fuel shut off valve. Change Spark Plug, perhaps to a hotter one. Did you change Needle and Seat? That is why fuel leaked. Check Valve...
Mulching creates a dense mat that harbours mold, disease and varmints. I do re mow most of my clippings as they are discharged onto unmown areas. When finished, a few passes with the sweeper and Done. I haul mine to the forest nearby.
You have made a great start in overhauling your engine. You are now overloaded with information. It appears to be a fuel problem. Exhaust glowing red hot indicates a very lean mixture or Cam timing problem. Check all Fuel lines. Blow them out (cap OFF tank) outside as fuel will splash. I...
I suspect the Second from Left Pully has a bent 'axle' . Remove the Pulley, get a piece of 1/2" pipe and carefully straighten the axle bolt. Vertical in all directions.
There is a linkage adjustment near the pedals that can be adjusted for optimum speeds both directions. Speaking about JD X320 and others. Try that Pedal height should be even or the Reverse somewhat higher. Stop mowing steep slopes. You can starve the engine from oil!
I think someone spiked that fuel before or after you got the unit. Check your enemies list and try to get it analyzed. New tank is the best way. Fuel lines too.
I digress. The Planet continues to Evolve as it always has. The Ice Age was only 15,000 years ago. Climate change is real but only a tiny percentage is caused by mankind. WE didn't start it and we Cannot stop it. A volcano emits as much crap in an eruption as we do in a Year. Learn to live...
A 21 or 22" will suit you well. You can often find suitable and reconditioned older mowers for $200 or less. Skip the Mulcher/bagger types.
1/3 acre ( 14,520 square Feet) minus home/garage, laneway, trees etc isn't much to mow. Older 3+HP Briggs and Stratton powered (not the newer Chinese...
Only mow when grass is Tinder Dry. After changing the oil, I remove my Deck in the Fall and turn it upside down on a gravel area and pour the used oil into it, swabbing it on all sides and protruberances. Leave it overnite to soak into rusted areas.
I believe at least 2 of the Flat Idler pulleys are loose and need replacement .
Put the front deck control arm back where it was and loosen off the Nut to replace it. Level the deck with front 1/8" lower than rear. Belt appears OK.
Leave Rim leak detection for a few minutes before looking. I use Windshield Washer fluid or Snoop if you can get it.
Don't forget the Tread and sidewall areas and Valve Core.
The Bore looks to be in very good condition. Be sure Valve Guide clearance is adequate. What gauge were you using to check compression. There must have been some! Carefully reassemble, Torque Gaskets and set valves per spec. It should run fine unless there is a camshaft problem. Be sure...