420cc powermore ohv

0.028" +- 0.003

See following for operator manuals for both the mower and the engine.

https://www.mtdparts.com/en_US/manualsearchresults

there is no connection between engine capacity and hp
in fact there is in reality no such thing as hp as it is actually torque or turning action around a centre
horse power was the ancient measurement of how many horses it took to lift a certain weight a set distance in 1 minute
as the cc is the swept volume covered by the top of the piston in a motion from tdc to bdc you will see that it is the stroke length that decides the amount of torque from the engine
to answer your question ( missing engine make and number of cylinders ) go google and type in ---engine specifications for ( missing details) and there you will see the cc , torque rating at set rpms and the theoretical HP

if it dies when it gets hot and starts after cooling. it is boiling the fuel. move the fuel line away from the heat at the engine. maybe put some foam wrap on it. ir the coil may be breaking down at hot temperatures. be sure the fins are clean so the engine can cool itself.

deck drive belt is 96.5 inches 42 Deck Drive Belt BRAND NEW Factory Part OEM Troy Bilt MTD Huskee and MORE

Genuine MTD 954 04045 Mower Deck Belt 42 5 available

same as mtd yardman craftsman etc

check craigslist for used, but who knows how long a used one would last. check out amazon for new under $140.

which tire?

You can find the full schematic and parts list for model model 313707. This link has everything on your machine. A full set of schematics and a full parts list for every part.
Briggs and Stratton 313707 0162 E5 Engine Parts

Check for gas contamination in the oil....if the oil itself it gas free....its likely a blown headgasket.

if its a briggs and stratton engine of older vintage always use straight 30 wt. about a litre will do then check level