Useful Tools
Two-stroke Premix Ratio Calculator
Dial in your perfect 2-stroke ratio.
Common ratios: 50:1 (modern), 40:1, 32:1 (older), 25:1 (vintage).
Required Oil
--- mL
Required oil volume.
Two-stroke Port Timing Calculator
Calculate port durations based on cylinder geometry.
Total travel of the piston (mm).
Center-to-center distance (mm).
Distance from cylinder top/deck surface to the port crown (mm).
Calculated Port Duration
---°
Opening/Closing Angle: ---° BTDC/ATDC
Compression Ratio Calculator
Calculate Geometric and Effective Compression Ratios.
Engine Geometry
Clearance Volume Components ($V_c$)
Measured volume of the cylinder head/dome (e.g., using a burette). Note: 1 cc = 1,000 mm$^3$.
The piston-to-head clearance at TDC (measured with solder).
Thickness of the head gasket.
Effective Compression Timing (TCR)
The height from the cylinder deck face down to the top edge of the exhaust port opening.
Altitude Compensation
Used to calculate relative air density for pressure compensation.
Compression Ratios
--- : 1 (Geometric)
--- : 1 (Effective/Trapped)
Altitude Effect
RAD: --%
--- : 1 (Equivalent Sea-Level CR)
Calculated based on measured head volume and effective swept volume.
Crank Balance Factor Calculator
Determine the target mass for crank balancing.
Piston Assembly Mass + Connecting Rod Small End Mass.
Crank Pin Mass + Big End Bearing Mass + Connecting Rod Big End Mass.
The percentage of reciprocating mass to be balanced.
Target Balancing Mass ($M_{balance}$)
--- g
Required counterweight mass equivalent at crank pin radius.
Engine Balance Calculator
Single Cylinder 2-Stroke Counterbalance Shaft Design
Engine Specifications
Component Masses
Balance Requirement
(Equals 12650 g-mm)
Shaft Geometry Designer
Cross-section view
Effective lever arm of the weight
Note: Standard 500cc 2-stroke design assumes a 50% balance factor on the crank to reduce vertical vibration, relying on the balance shaft (rotating oppositely at 1x crank speed) to cancel the resulting horizontal couple. This calculator assumes the balance shaft rotates at engine speed.
