Bored something over? How many CCs

[Ryan]

I know this has been posted before but I can't seem to find the fourm. im very curious on this. With all that Bore .10 over or from so on..... How do you do the math to figure out the estimate of how many CC's the motor will put out :confused2 ?

[Wheelie]

Pi multiplied by the Radius of the piston squared, multiplied by the length of the stroke. Take that result and multiply it by .001.

Example for 400ex: 85mmx70mm--

42.5x42.5x3.14x70x.001=397.01375cc'c

I hope I explained that well enough.

[BlazingYamahaYz]

i didnt think there was a way to really calculate true cc increase, unless its like a 440 kit or something...learn new things every day i guess...:)

[Burden7]

Here is the formula that I use:

Bore * Bore * Stroke * .000786

[Ryan]

Originally posted by Wheelie
Pi multiplied by the Radius of the piston squared, multiplied by the length of the stroke. Take that result and multiply it by .001.

Example for 400ex: 85mmx70mm--

42.5x42.5x3.14x70x.001=397.01375cc'c

I hope I explained that well enough.

Thanks for the help. Im still a bit confused. Where did you come up with some of those numbers? (42.5x42.5) 70x.001 :huh :scary:

[sly400ex]

Originally posted by Wheelie
Pi multiplied by the Radius of the piston squared, multiplied by the length of the stroke. Take that result and multiply it by .001.

Example for 400ex: 85mmx70mm--

42.5x42.5x3.14x70x.001=397.01375cc'c

I hope I explained that well enough.

From his quote....



Pi=3.14

Radious of piston squared, which would be 42.5 to the second power, or 42.5 times 42.5

Then by .001


By the length of the stroke..

[Ryan]

in the beginning numbers, Its 42.5x2 rather then 42.5x42.5? 42.5x42.5=1806.25 so it must be 42.5x2 since that comes out to 85.

Since were on the math subject, I swore if it was 42.5 to the second power, it would be 42.5x42.5 again :huh .

[sly400ex]

Oops, you're right, I just corrected it.;)

[Ryan]

I was just messing around with and read this thread over and over again and I think I finally got it :blah .

Divide the Bore in half. 85mm/2=42.5 . Then 42.5x42.5x3.14xthe stroke (70mm)x.001 . Thats alot of numbers :o .

Thanks for the help guys.

BTW, if I wanted to find how much cc it would have after boring it .40 over, would that be .040 instead of .001?

[Burden7]

if you know the Bore (in mm) and the Stroke (in mm) then all you have to do is put the numbers in my formula that I supplied in an earlier post. I think it is a pretty easy formula.

[Ryan]

Originally posted by Burden7
if you know the Bore (in mm) and the Stroke (in mm) then all you have to do is put the numbers in my formula that I supplied in an earlier post. I think it is a pretty easy formula.

I was just reading your earlier post and I was wondering where the number .000786? Do you use this same number in any formula if you wanted to find the cc's :confused: .

BTW, your way from "Wheelie's," The numbers are a bit different. It still is 397cc but your formula rounds to 398 :huh .

[Burden7]

I'm not for sure where the number comes from. I think it is some sort of conversion number. I got this formula from somebody else and it works everytime. You can only use the (.000786) number in this particular formula. I have never had the need to use a different formula.

[Ryan]

ok thanks. I don't think I can use that formula unless it was a 400ex though. These numbers are really confusing.

I wanna figure out how I add .40 to "Wheelies" formula to get the cc of the motor.

[Burden7]

I don't understand how this is confusing?? The formula that I have will find the CC's of any single cylinder engine. If you want to find the CC's of a banshee, or any multiple cylinder engine, just multiply the result by the number of cylinders there are.

Do you know the size of piston that is .40 over? I'm not for sure if it is an 86mm or 87mm piston. For example if you want to find the CC's of a 400ex with an 87mm piston, the formula will be as follows:

87*87*70*.000786 = 416.45 CC

Class dismissed!

[Ryan]

Originally posted by Burden7
I don't understand how this is confusing?? The formula that I have will find the CC's of any single cylinder engine. If you want to find the CC's of a banshee, or any multiple cylinder engine, just multiply the result by the number of cylinders there are.

Do you know the size of piston that is .40 over? I'm not for sure if it is an 86mm or 87mm piston. For example if you want to find the CC's of a 400ex with an 87mm piston, the formula will be as follows:

87*87*70*.000786 = 416.45 CC

Class dismissed!

I thought you said before that this number ".000786" will only work for the 400ex engine? It really doesn't matter which formula I use really.

[Burden7]

The only time I said anything about a 400ex, was in my last post. And yes, you can use either formula. You started to get a little confused, so I thought I would give you an easier one to use.

[Ryan]

ok thanks.

Heres another question for you :rolleyes: . If I were to bore my cylinder .20 over, would this put me up 1mm piston size :huh . or how does that go :confused: .


Im not good at explaining things ;) .

[Burden7]

Yes, I believe that for every .20 over it is 1mm in piston size.
If you are going to buy an oversized piston, I would buy it first and then take the piston and the cylinder to somebody that can bore it to the size of the piston with the required tolerances.

[Ryan]

Originally posted by Burden7
Yes, I believe that for every .20 over it is 1mm in piston size.
If you are going to buy an oversized piston, I would buy it first and then take the piston and the cylinder to somebody that can bore it to the size of the piston with the required tolerances.

Well I don't have to do that. I was just wondering how all this math stuff works. Im all outta questions :cool: . Thanks alot for all the help.