Calculation Formulas
Stock Briggs & Stratton 5 hp. specifications:
Deck height: 6.2835"
Rod length: 3.8750"
Compression height: 1.1900"
Rod bore (crank): 1.0010"
Rod bore (wrist pin): .4910"
Cylinder bore: 2.562"
Stroke: 2.4370
Measuring Stroke
Stroke is measured from the center line of the crank bearing journal to the center line of the rod journal multiplied by 2.
Measuring Deck Height
Deck height is measured from the center line of the crankshaft bore to the deck of the block.
Measuring Compression Height
Compression height is measured from the center line of the wrist pin bore to the top of the piston.
Calculating Cubic Inch Displacement (cid)
To calculate cubic inch displacement (cid):multiply bore x bore x stroke x .7854example: 2.562 x 2.562 x 2.437 x .7854 = 12.5633 cid
Rod Length & Compression Height - Made Simple
Calculating Rod Length
To calculate rod length:subtract deck height - (stroke divided by 2) - compression height.example: 6.2863 - (2.437 / 2) - 1.190 = 3.875 rod length
Calculating Compression Height
To calculate compression height:subtract deck height - (stroke divided by 2) - rod length.example: 6.2835 - (2.437 / 2) - 3.875 = 1.190 compression height