Two Stroke Design Software

The following are Excel spreadsheets for different aspects of 2 stroke design/modification. If you don't have Excel or have a version of it that doesn't work with macros (needed for ECcalc, Porting calc, Crank Calc) then you can buy Microsoft Office 365 for $70 at

Expansion Chamber Analysis & Design
This is a complex return wave simulator that allows you to analyze an existing pipe or design your own for the desired powerband and top RPM.
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Porting Calculator
Calculate the needed exhaust and transfer port durations to match the desired peak power RPM. This is not a rehash of the old outdated port time*area formulas but rather it relies on the true blowdown time (the time it takes for the exhaust pulse to go to zero pressure). read more

Jetting Calculator
Calculate the best needle, slide cutaway, and main jet based on the carb flow velocity.
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Squish Velocity
Calculate the exact piston/head clearance needed for the right squish velocity for max power. read more

Crank Balance
Calculate the right size and placement of counter-balance holes in the crank wheels for less vibration. read more

Yamaha Energy Induction System (boost bottle)
Calculate the correct dimensions for the bottle to resonate right at the RPM range before the engine gets "on the pipe" which is when there is a bad power dip which the bottle counters. read more

2 Stroke Fuel/Oil Ratio Calculator
Calculate the needed fuel/oil ratio dependant on your oil, type of riding, max RPM, and type of cylinder cooling. This uses my formula that goes mostly by the viscosity and viscosity index. read more


Author: Michaael Forrest