[newkid17]

ok so ii built a weedwacker engine that runs on compressed air yesterday, it runs ok but i have it set up so that the air comes in from the spark plug hole, so i am thinking that there is still compression resistance when the piston comes back up, therefor the piston is not reaching top dead center. it really shakes when its running so i am thinking that because the piston is not going all the way up that the engine is running back and fourth( left and right). anyone ever made one of these before? and suggestions on how to get the air out of the top of the piston when it comes back up?

Bobby