Engine displacement is the volume, measured as the space between the top of the piston at bottom dead center (BDC) and the top of the piston at top dead center (TDC). The combustion chamber is in the head and is not part of this calculation. This is calculated using the standard cylinder volume formula. (Scroll to the bottom for formula details.)
This chart describes the engine displacement based on Bore and Stroke.
- Measurements are in millimeters (mm or mil).
- Bore is the diameter of the engine cylinder.
- Stroke length is the distance travelled by the piston during each cycle of the engine.
- Stroke is affected by the swing of the crankshaft during a rotation and the connecting rod length.
- Q - What is a 4 mil or 10 mil engine?
A - Stroke length is +4 millimeters or +10 mil over stock stroke of 54mm.
Check out our blog: Types of Banshee Engine Builds - Stock, Small Bore, Big Bore.
- Stock Length crankshaft can also be an OEM crank that has been trued and welded. We true and weld any OEM crank involved in an engine build where the engine case has been cracked open.
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Cylinder Type Needed
- Chart Colors are based on the Cheetah Cub engine cylinders manufactured by Cast Precision Industries, Inc (CPI).
- CPI also manufactures Serval and Wampus Cylinders.
- Driveline Performance offers Assassin and Assassin-II cylinders, and we have found them to also be a quality engine component.
- Here's a link to our blog article: Which Cylinders Do I Want? This may help you understand why you might select one over the other cylinder lines.
For additional information, check out our blog articles in: Banshee Engine Building & Performance.
Calculation Details
The above chart helps us (and you) to quickly calculate the engine displacement. Our numbers may be off by a smidge due to rounding.
If you want the actual formula, here's the math to Calculate a Yamaha Banshee's Engine Displacement in cubic centimeters (cc) using the standard cylinder volume formula:
CC = (Bore Diameter / 2)² × π × Stroke × Number of Cylinders / 1000.
The Formula Breakdown
- Bore: The diameter of the cylinder measured in millimeters (mm). Standard stock Banshee bore is 64 mm.
- Stroke: The total travel distance of the piston from Top Dead Center (TDC) to Bottom Dead Center (BDC) in millimeters (mm). Standard stock Banshee stroke is 54 mm. The stroke is changed by selecting a crankshaft with a different swing and rod length.
- Number of Cylinders: The Yamaha Banshee is a twin-cylinder engine, so this value is 2.
- π (Pi): Approximately 3.14159.
Step-by-Step Calculation (Stock Banshee 350)
- Divide the bore diameter by 2 for the radius: 64 ÷ 2 = 32 mm
- Square that number (r²): 32 × 32 = 1024
- Multiply by π (or pi): 1024 × 3.14159 = 3,216.99
- Multiply by the crankshaft stroke length: 3,216.99 × 54 mm = 173,717.46
- Multiply by the number of cylinders (2): 173,717.46 × 2 = 347,434.92
- Convert cubic millimeters to cubic centimeters (divide by 1,000): 347,434.92 / 1000 = approximately 347.4 cc (commonly referred to as a 350 cc engine).
Modified and Stroker Engine Examples
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Bored Over (e.g., +0.04", or 65 mm bore) with stock crank stroke comes out to approximately 358 cc:
(65 / 2)² x pi x 54 x 2 / 1000 ≈ 358.38 cc
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4-Mil Stroker Crank (stock 64 mm bore with +4-mil or 58 mm crank stroke):
(64 / 2)² x pi x 58 x 2 / 1000 ≈ 373.17 cc -
4-Mil Stroker Crank with Small Bore (65.5 mm bore and 58 mm stroke):
(65.5 / 2)² x pi x 58 x 2 / 1000 ≈ 390.87 cc (or 391 cc, rounded up) -
4-Mil Stroker Crank with Big Bore (68 mm bore and 58 mm stroke) (popular 421 cc build):
(68 / 2)² x pi x 58 x 2 / 1000 ≈ 421.28 cc
Note about the Calculations: I double-checked the formula and examples, and they worked out. BUT -- if you find something that needs corrected, please do let me know. ~Janel 😉