just bored my 250r .50 over could it be like 258 or somrthing like tht thnks everyone

 

hmmm .040 over is +1mm i think so .050 should make your bike a 260 i think, not sure but its def either a 258-260, what size is the 250r exactly? like a 247?

 

im not sure to be honest but i think 258-260 is good im along time drag racer and was just wondering about new size thnks lot for your input

 

I can't tell you exactly because I don't know the stroke of the 250r. But here's how to do it.

Square the bore diameter and then multiply it by .7854. This will give you the area of the bore. Then multiply that by the stroke. Divide the answer by 1000 and you'll have the volume (displacement) of the cylinder.

(((bore x bore) x .7854)) x Stroke)/1000

I have a Honda 250x. The bore is 74 mm and the stroke is 57.3 mm. So, 74 x 74 = 5476. Then 5476 x .7854 is 4300.85. Then 4300.85 x 57.3 = 246438. Then 246438/1000 = 246.438cc.

(((74 x 74) x .7854)) x 57.3)/1000

 

I guess I should also mention that to convert inches to mm, multiply your inch measurement by 25.4.