With regular oil & filter changes at required intervals with proper quality engine oil and not lugging or over revving the engine.
And engine knock is normally caused but I worn crankshaft bearing or rod bearing.
A knock probably means a bearing has already gone.
Probably a bad rod bearing
The engine will have a distinct "Knock" while running.
if its a loud knock from the bottom end, DO NOT run the engine, it is likely a spun bearing; have a professional look at it
A loud knock is usually associated with a rod bearing. The rod connects the crankshaft to the piston. If a rod bearing went out, possibly from an oil pump going bad, it would stall out the motor.
A lower engine knock is usually a bad bearing on the crankshaft. Could be a rod bearing or a main bearing.
A spun--Bad rod bearing. NO OIL PRESSURE.
If it is more of a ping than a knock then just try running some higher octane fuel in it. If is more of a knock it could be a rod or crankshaft bearing. If it is definitely a knock you should get it looked at right away.
sounds like a crankshaft bearing, or a piston rod bearing are worn, broken or missing.
remove brake drumremove bolts holding bearing to rear spindlebig hammer to knock it out of the spindleif no bolts then look for large clip around the hub bearing to remove
You will want to bring in a licensed carpenter and perhaps a structural engineer.