about 33 mph
The correct spark plug for a 5 hp. Tecumsen 4-cycle motor is Champion J-8 (RJ17LM). The plug gap is 0.030 in. (0.76 mm)
That is the main jet needle valve.
Brigg's and stratton 5.5 hp on the craftsman push mower your gap tool set the gap at .025-030 for briggs 5 hp
If that is a 5 horsepower Tecumseh engine - ( .030 inch )
.020in
.030
.035
45 to 60 thousands,
5 to 14 thousandths
An Autolite 258 is the recommended spark plug for a 6. 5 horsepower Tecumseh engine. A Champion RJ19LM also is recommended by the manufacturer.
twenty eight ounces