Yup... flip that thing upside down and use a 10cc syringe to fill the combustion chamber and subtract with what's left in the syringe to get your cc's.. it can vary as much as 7.5cc all the way past 10cc, they are that much different. you'll need the head off and preferably a sheet of plexiglass over the combustion chamber, sealed with grease and with a hole drilled for the syringe for the most accurate readings since you'll usually get a "dome" of liquid above the top when you try to fill it.