MX | ROADRACE | KARTING | MOPED
This manual describes how to measure the volume of a combustion chamber, including the volume of the spark plug hole.
To measure the cylinder head volume you'll need a pipette and tap. We have these in stock for you:
Remove the cylinder head from the cylinder and make sure that the piston and combustion chamber are clean.
Check the piston height and make sure this is correct (according to the piston height indicated on the insert box). In this example the piston height is -0.5mm, which means that the top of the piston is 0.5mm below the cylinder deck. Want to know how to measure the piston height? Check our piston height measure manual.
Mount the cylinder head on the cylinder and make sure to tighten the bolts. Then move the piston, by rotating the crank, to top dead centre (TDC). The piston is at TDC when it's at the highest possible point in the cylinder.
Fill the pipet with liquid to 0ml level. When liquid is in the pipet, it has a curve at the top. The liquid level is determined by reading the bottom level of the curve of the liquid.
Fill the combustion chamber with liquid till the top of the park plug hole. It will form a meniscus or curvature.
If meniscus is concave, or pointing downward, then bottom of meniscus is below top of the spark plug hole. This is not correct, adjust fluid level with more liquid.
Below you can see that liquid is below top of the spark plug hole, which is not correct. You can click on the image to enlarge it.
Below you can see that liquid is leaking over the top of the spark plug hole. This is not correct. Use a pipet to draw some liquid out.
The correct level of liquid is when there is a convex meniscus, or upward pointing meniscus. Liquid is a little bit curved over the top of the spark plug hole.
Below you can see that liquid is a little bit over the top of the spark plug hole. This is correct.
Now you can read the volume on the pipet graduation. Measured volume in this example (bottom level of the liquid curve) is 11.40ml = 11.40cc with a piston height -0.55mm.
Measured volume of 11.40cc is not the volume of solely the combustion chamber!
Measured volume is volume of combustion chamber including volume of the spark plug hole.
If you've measured your piston height, you can use our insert calculator to calculate the insert volume and actual squish. This can variate from the values indicated on the insert box when you have a different piston height then indicated as well on the same box.