Two Stroke Design Software

The following are spreadsheets for different aspects of 2 stroke design/modification. If you don't have Excel or have a version of Excel that doesn't work with macros then you can buy Microsoft Office 365 for $70 at These are the ones that can function manually without using macros by using Open Office: Jetting Calc, Squish Calc, Crank Calc, Ratio Calc, and Boost Bottle Calc. Click here to get a free download of Open Office. Here's some helpful videos: Intro to using spreadsheets, Overview of these spreadsheets

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 This is not a rehash of the old outdated port time*area formulas but rather it relies on the true blowdown time (the time it takes for the exhaust pulse to go to zero pressure).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 for perfect air/fuel ratio thru the whole throttle opening range.
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Squish Velocity
Calculate the exact piston/head clearance at the squish band 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 oils viscosity and viscosity index. read more


Author: Michaael Forrest