I know it's been posted in several area's with some slightly different calculations, I have tryed to figure CC's with known engines using bore x bore x stroke x .7854/.061 and x.061 as posted. What am i doing wrong? I'm not the sharpest knife in the drawer but geez.
Someone have an easy way to measure/calculate-Thanks

That's it. (Bore x Bore) x stroke x .7854 equals cubic inches. That divided by .061 equals cc.

Example:

Bore 1.25"
Stroke 1.10"

1.25 x 1.25 = 1.56
1.56 x 1.1 = 1.72
1.72 x .7854 = 1.35 cubic inches
1.35 / .061 = 22 cc

AV8TOR

Thanks Av8tor, I must be measuring wrong. I'm certain the engine is a 21cc. The bore of the cylinder measures 1.267 the stoke is 1.001.
Hard to measure stroke-
i know what i'm doing wrong-Like i said "dull knife"

AV8TOR

I guess that's another way to skin a cat.

I've always used the traditional: pi x radius2 x stroke = 3.14 x (1/2 bore x 1/2 bore) x stroke.

3.14 x (0.625 x 0.625) x 1.1 = 1.349 cu. in.

Yep, that works too...

AV8TOR

Use ratio 25cc=1.5ci. If you know either your cc or ci you can use this formula. Enter your info in
-
X X
the X and cross multiply and divide.
-Gary