Champion CJ8
The proper spark plug for 4hp Briggs & Stratton is a J8 which I use in all my motors.
The B&S 797235 is a resistor plug. You can use a Champion RC12YC.
A Champion CJ8Y or J19LM will perform fine
You could try cleaning the spark plug. That worked for us. Take the spark plug out with a wrench and use sandpaper to clean it.
If you have a different brand spark plug, Champion will have a cross reference. You just need the number from the plug. If you do not have that, you will need the model number from the engine. Briggs and Stratton built a LOT of engines with customizations that may use several different spark plugs. 342 cc is simply not enough information.
You can use a Champion RC12YC, available @ any car or farm store.
I am asking the question. So there is no point in asking me to answer the question if I do not know the answer.
If you mean that the wire came out of the boot, then pull the boot off of the spark plug and use a spark plug socket to remove the spark plug.
Remove the spark plug wires from the spark plugs, use an extension for your Allen wrench, and use a spark plug socket to remove the spark plug.
The best way is to use the spark plug socket out of the factory tool kit. If you do not have that use a normal 5/8" socket to loosen the spark plug. Use the spark plug wire to snap back on after the plug is loose and pull it out. The spark plug is at the very top of the engine, the spark plug wire is a real good indicator of its location.
To Determine what spark plug is in your 16hp enging you would need to be more specific. It could have a Briggs and Stratton engine or it could have a Kohler engine. Both engines use different spark plugs. The spark plug for the Kohler engine is part number 32295-1. The part number for the B&S engine is 43591-7
If it is a 3.5 hp I usually use a j-8 or equivalent seems to work well in them. hope this helps