If you do not rotate the cylinder and piston you will have higher compression on the reversed engine and you wil have to richen this engine a lot and it will never run the same as the normal running engine. I have done it with my dle55 and have put in a lot of time to figuring out. Also keep in mind that adjusting the ignition timing will make a lot of difference in rpm. If you don't adjust the timing exaclty right on the reversed engine this engine will lose easy 400rpm. If you dont believe me than try rotating a normal engine clockwise. You will notice a compression difference when rotating it by hand in the opposite direction.