700 Redhead compression ratio

Vincent

Vincent

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Anybody ever measure the volume of the combustion chambers and get some real world compression ratio numbers?

Two months ago I removed the middle layer of my headgasket. I calculated that I removed about 1cc of volume. But I'm missing some head volume numbers to calculate how much static compression I gained.

I should have taken the time and measured it myself but I was in a rush (for no reason) and I didn't do it.
 
Have you pulled compression with it off? I have wondered what a read head pulls with a peeled head gasket. My mtn max pulls 145psi on all cylinders and I'm wondering if someone peeled the head gasket before I bought it.
 
Backwoods M Max said:
Have you pulled compression with it off? I have wondered what a read head pulls with a peeled head gasket. My mtn max pulls 145psi on all cylinders and I'm wondering if someone peeled the head gasket before I bought it.
Click to expand...

I did measure it before and after.

Gained about 7 psi per cylinder. My numbers are not as high as yours.
 
Another interesting thing to consider would be the "Dome" of the pistons. Not sure how one would measure that.

It would also be cool to get some info on the SRXs and Vipers. While we are at it, why not the 500 and 600 twins to.
 
Vincent said:
Another interesting thing to consider would be the "Dome" of the pistons. Not sure how one would measure that.

It would also be cool to get some info on the SRXs and Vipers. While we are at it, why not the 500 and 600 twins to.
Click to expand...

I saw a recent thread about low compression in a srx and someone said around 110 was normal???? The guy had 90 in one cylinder and 100 in the rest and people were saying it was rebuild time
 
My sled is currently at 127-130- 126 psi. And it's an old high mileage 700.

As much as cylinder pressure comparison is cool and I'd like to gather more info on that too, it's not the information I was looking for.

Im surprised how i can't find any info on compression ratio numbers. I really regret not taking the time to measure my engine's combustion chamber volumes when I had the chance.
 
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I realized there is two ways of calculating 2 stroke compression ratio. One is the full cylinder stroke vs combustion chamber volume, the other is stroke volume from the point when the exhaust port is fully closed vs combustion chamber volume. I believe the first is called static and the second one is dynamic, but I mite be wrong.

Some simple calculating based on the very limited info I have. Using the Static concept.

698cc / 3 is 232.7cc
I threw some numbers around and if our combustion measured 35.25 cc you end up with,
(232.7 + 35.25) / 232.7 = 7.6 C/R

So if I remove my 10 thousand middle gasket from the equasion, so about 1cc

(232.7 + 34.25) / 34.25 = 7.79 C/R

So in theory removing the middle headgasket gains you almost . 2 more C/R

I welcome anyone to add or correct this. It's all just for fun.
 
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