ORIGINAL: cutarug
My question is does the compression get better as you run it in and how long does it take.
I tested the ring in the bore and there is little to no gap but I expected more compression than I got.
I took the ring off the piston and reduced the thickness a bit on some fine wet and dry paper as it was just a bit thicker than the original and I will test it again.
I hoped to get 7700 from it which would fly the Sparrow hawk with about 16 lb of thrust.
Any suggestions for developing more compression.
The compression and power will improve as you get more run time on it. In general I've heard that gassers will improve power output over the course of several gallons of fuel burned, although I've only qualitatively observed this.
The best thrust I've gotten out of a Ryobi 31 has been 15 lbs of thrust based on a sample of two, one early model single runner transfer port, single ring piston and one dual transfer port two ring piston. 16lbs of thrust is an admirable target and might be possible but it will be at the very max of it's capability from my experience. In order to get this kind of power a tuned pipe (aka expansion chamber) will probably be necessary and I've never made one up for mine.
diceco