# Thread: look for a formula

1. ## look for a formula

I was just checking out our awesome tech section. I was wondering is there a simple formula for figure out the cc's of a craft? I was wondering about my SLX 779 cc's. Std bore is 71.3 mm and it's bored over 1.5 mm, 65 mm stroke, heads un-installed 28.5 cc's, and installed volume is 23.9 cc's. I could not even figure how they got the 779 cc' never mind throwing in the 1.5 mm over sized pistons. I am assuming it at least 800 cc's.

2. 811.8 cc's Nut.

3. Wow, that's bigger than I thought than. Thanks man I couldn't figure that one out to save my life.

4. I always wanted to know this formula as well.
So I keep doing this calculation and I come up with 811684 and am wondering where the difference is, not that it matters, it just drives me crazy. Also I end up with a number of 811674..........,how would you know how many positions to move the decimal?? Obvously in this scenario you know it needs to be roughly 800 but I just wonder why the finished calculation is not in the formula or did I miss something?

.7853981.......
X 5299.84= 4126.4845........
X 65= 270561.4991......
X 3= 811684.49744856.......

5. maybe with how many decimal places you actually use pi for? I got 811273.

6. It should be to 1 place because in Nuts measurements its to 1 decimal place/pi would be 3.14 but you always go to the fewest places given-811684.4974=811684.5mm

http://www.ducatitech.com/info/bore_stroke.html

8. compression ratio is 12.31 to 1 if you were wondering.

CV+CCV/CCV=Compression Ratio (Uncorrected or full stroke or swept volume whatever you want to call it)

I have lots of others in my head as well. if you measure you port height from the top of the cylinder to the top of the exhaust port then subtract your deck height i can tell you correct compression ratio as well.

9. Thanks guys! I was stumped. I'll be writing these down and putting them in the manual for sure.