Calculate CC's

[eprovenzano]

How do you calculate the CC's of an engine that's been bored over. My cylinder is be bored to accept a 86.00mm piston (4th over) running on a stock crank. I was just curious as to the CC's of the engine.

[trailrider894]

That would be a 402cc

[CJM]

Originally posted by trailrider894
That would be a 402cc

86mm piston is a 406, gotta remember the engine itself is designated 400cc but in reality is 397cc.

[trailrider894]

Originally posted by CJM
86mm piston is a 406, gotta remember the engine itself is designated 400cc but in reality is 387cc.

86.5MM is 406cc. From my understanding... on how i did the math.

Standard bore- 397cc or 85mm

402cc- .040 over or 86mm

406cc- .060 ever or 86.5mm

416cc- .080 over or 87mm

426cc- .120 over or 88mm

440cc- .160 over or 89mm

also...

440cc with an extra 4mm stroke = 460cc

416cc with an extra 4mm stroke = 440cc

[CJM]

Right off wisecos site:

85.5 is 402
86 is 407 (406 depends on which piston maker)

[rubbersdown]

The formula and math is as follows...

pi (1/2 bore) ^2 * stroke

or to make it easier...

Pi X R X R (R squared) X H

I'll do it for the 400ex

So get the bore in cm, divide by 2. 86mm = 8.6cm, /2 = 4.3 square it, = 18.49, times Pi, 18.49 X 3.14159 = 58.08

58.08 X stroke in cm, 58.08 X 7.0 = 406.56cc's

The math says a stock stroke with an 86mm piston is 406.

[trailrider894]

Originally posted by rubbersdown
The formula and math is as follows...

pi (1/2 bore) ^2 * stroke

or to make it easier...

Pi X R X R (R squared) X H

I'll do it for the 400ex

So get the bore in cm, divide by 2. 86mm = 8.6cm, /2 = 4.3 square it, = 18.49, times Pi, 18.49 X 3.14159 = 58.08

58.08 X stroke in cm, 58.08 X 7.0 = 406.56cc's

The math says a stock stroke with an 86mm piston is 406.

Hmmm... thanks guys. Not sure how the site i got that from was wrong. Thanks for the new knowledge!!! :)

[eprovenzano]

Thanks guys. I appreciate the lesson.