2 Stroke Carburetor Sizing

I found out that the formula manufacturers have used to figure out what carb diameter to use is not as simple as .8 x square root(cc x RPM/1000). They went by the flow velocity with higher velocities being better for engines being used mostly at mid range RPM. Engines that mostly used high RPM were given larger carbs for lower flow velocities. The chart below generally shows what they did:

This is handy to know if you want to turn a street bike into a racing bike or a racing bike into a trail bike. You can click here to download my Carb Size Calculator (Excel spreadsheet) that tells you the desirable carb size dependent on engine size and intended use. Just enter the needed data into the light blue cells and the calculated results will display in the other cells.

Click here for a list of my 2 stroke calculators.