Added combustion chamber recesses to the rotor, spark plug holes and intake/exhaust ports to the housing. Technically the ports should take a 90 degree bend and exit out the side, but then you wouldn't be able to watch the rotor movement from the crank side of the housing.The crank and eccentric have been modified for a looser fit, the originals weren't working for me. Fit the rotor into the housing, pop the crank through, put the eccentric in. If the crank and eccentric are too loose, download the original ones from jag.If you were one of the first 70 or so people to download this, you may have noticed the eccentric and crank were extremely loose, because they were at 3/4 scale. Oops. Scale the files up by 1.33333... before printing or just download the fixed versions.