UCCR

[udontknowme]

for the math wizards how do you figure compression ratio with no liquid ? and theres no cc stamped on the dome

[JOHNNY FIVE]

Is the stock stroke 72mm?

[JOHNNY FIVE]

Is the stock stroke 72mm?Also my piston says 75.94,so im assuming my bore is 76mm?

[acecarlos]

Yup, stock stroke is 72MM, 75.94MM piston is a 76MM bore.

As far as determining your compression, you need to determine the Squish, Piston Dome Volume and Dome CC's..if determining the Dome CC's using pure math, that would be difficult. The biggest issue I see is determining what the dimensions are in the machined Dome; the radiuss of the cavity, depth, angle, all would need to be known accuratly.

Using the "liquid" method is far easier than using pure math. One option would be to model the Dome & Squish using a CAD or Modeling program, then machining to the exact model. The CAD or Model program would let you see the volume of the Dome, as long as it was machined properly, it would be an accurate method.

Stick with the "liquid" method; perform a full UCCR...much easier and very accurate.

Carlos.

[udontknowme]

math would be very lengthy. not sure why anyone would even try. found something regarding this subject on another forum. one guy says he measures it with oil. some bonehead name alisobob basically calls him a idiot and says math would be easier. shook my head for 20min when i read that. about 1/4 down the page check it out. funny stuff Bannedcr500riders.com :: View topic - Piston and Cyl pics...

[JOHNNY FIVE]

Is the "squish" the gap between the piston at top dead center and the head?

[acecarlos]

Squish or Squish band is the portion nearest the head Dome when the piston is at TDC. On 250R's, normal Squish clearance will be between .040"-.060" (1MM to 1.5MM). For certain applications, Squish clearance can be set as low as .020" (.5MM) or as high as .080" (2MM) or more.

Carlos.

[JOHNNY FIVE]

Thanks for the insight.

[acecarlos]

My pleasure...

Carlos.

[mennis1971]

Alisobob is anything but an idiot. Probably to smart if anything and that's a very tightknit group over there. It's a completely different site over there for sure. Btw I loved the "self smart" trailor park boys video. Those guys really know cr500's. Personally I like carlo's method better, but all I have ever measured was just the compression ratio in psi and never bothered with anything else and probably won't.