Useful Tools

Two-stroke Premix Ratio Calculator

Dial in your perfect 2-stroke ratio.

Target Ratio (X:1)

: 1

Common ratios: 50:1 (modern), 40:1, 32:1 (older), 25:1 (vintage).

Fuel Volume

Required Oil

0.0 mL

Please enter a ratio and fuel volume above to calculate.

Initializing Firebase...

Two-stroke Port Timing Calculator

Calculate port durations based on cylinder geometry.

Piston Stroke (S)

Total travel of the piston (mm).

Connecting Rod Length (L)

Center-to-center distance (mm).

Port Height from Deck (H)

Distance from cylinder top/deck surface to the port crown (mm).

Calculated Port Duration

---°

Opening/Closing Angle: ---° ATDC/BTDC

Initializing Firebase...

Crank Balance Factor Calculator

Determine the target mass for crank balancing.

Reciprocating Mass ($M_{rec}$)

Total mass of the piston assembly (piston, rings, pin, clips) PLUS the **Small End Mass of the connecting rod**. The rod's mass is split between rotating and reciprocating portions based on how the weight acts relative to the crank throw.

Rotating Mass ($M_{rot}$)

This mass rotates entirely with the crankshaft. It includes the mass of the crank pin, the big end bearing (needle rollers, cage), washers, and the **Big End Mass of the connecting rod**. The rod's mass is typically split by finding the center of gravity or using a knife-edge jig to determine the portion of the rod mass that acts as rotating (big end).

Target Balance Factor (BF)

The percentage of the reciprocating mass that is chosen to be balanced by the crank's counterweights. Lower BF (40-50%) generally favors high RPM smoothness; higher BF (55-65%) favors low-to-mid RPM comfort.

Target Balancing Mass ($M_{balance}$)

--- g

Required counterweight mass for 55% balance factor.

Engine calculations are client-side.

Compression Ratio Calculator

Calculate Geometric and Effective Compression Ratios.

Engine Geometry

Cylinder Bore Diameter (D)

Stroke Length (S)

Clearance Volume Components ($V_c$)

Combustion Chamber Volume ($V_{cc}$)

Measured volume of the cylinder head/dome (e.g., using a burette). Note: 1 cc = 1,000 $mm^3$.

Squish/Deck Gap ($H_{squish}$)

The piston-to-head clearance at TDC (measured with solder).

Head Gasket Thickness ($T_{gasket}$)

Thickness of the head gasket.

Effective Compression Timing (TCR)

Exhaust Port Height ($H_{exhaust}$)

The height from the cylinder deck face down to the top edge of the exhaust port opening.

Altitude Compensation

Altitude Above Sea Level

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.