Why is the engine only firing on one side
You can find the operator's manual for that engine at www.briggsandstratton.com. You will need to contact the manufacturer of the mower for the lawn mower owner's manual. Briggs and Stratton did not amke that mower, only the engine.
That depends on the mower and engine. I have Cub Cadet rider with a 16 hp Kohler engine that does call for 10w30. A lot of others call for sae 30 only.
If it is an 1989 engine the firing order is 123456. with #1#3#5 on the passenger side of the engine. that is the only choice.
No. Check oil only when engine is off.
Only if it is a two-stroke (two-cycle) engine.
My Huskee mower will not mow in reverse due to a switch that kills the engine if the blades are engaged. This is very inconvenient. I removed the switch and it now mows in reverse. Do this at your own risk. I am the only person who uses my mower and it will be reinstituted when I sell the mower.
A gas only engine has a spout where oil is added to the engine. If there is no spout, then it is a gas/oil engine. FYI - gas only engine is a four-stroke (four-cycle) engine and the gas/oil engine is two-stroke (two-cycle).
Oil is a lubricant that helps to keep an engine running. If a person runs a lawn mower without oil, the mower will run, but it will cause problems like stalling out, or worse. +++ Its engine will run, but only for a very short time before seizing, probably ruining it.
if it is a 2-stroke engine then it only can be 1 of 3 things, the spark, the fuel or the compression.
The fuel filter for a Honda self propelled push mower with a Briggs and Stratton engine is located between the fuel tank and the carburetor. The fuel filter is only about one inch long.
You have water in your oil. Possibly from condensation. Run the engine only long enough to warm the oil and change it.
It's a safety feature of the mower. Usually this only happens when the blades are engaged.