I am in the process of rebuilding the top end of my 91' DR 650 and have a question regarding volume. If I get it overbored by 1mm, what will the cc be? Also, what about going 2mm over? My stock piston and cylinder is a bit worn and I think I am going to have to go up. Any information would be helpful. Thank you.

{[(stock bore (mm) + 1mm)/2]^2}* 3.14159]} * Stock stroke(mm)}= cubic mm

divide cubic mm by 1000 = cc

Stock is 95 X 90.4 = 641cc. 96 =654cc, 97 = 668cc. Other things being equal this would be a bit under 1/2 HP per each MM bore increase.

who makes big bore kits for DR650?

google wasn't much help, except in finding this thread.....

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