McCoy 0.19

3 srews hold the cylinder on a Mccoy. I don't think it can go on backwards due to the way the screw holes are triangulated. I presume your talking the Mccoy red head stunt? Many issues are apparent with these engines. I would highly suggest if all other factors are good, plug, fuel, needle valve not blocked to take a look at the head gasket. The head gasket and the cylinder base gasket were fibre paper. You could remove them both which can be a job in itself if their stuck hard to the surface. I would use high temp Permatex Ultra Copper in place of the new gasket. Replace all head screws using 4-40 socket heads. The 3 longer screws that hold the cylinder in place may need approx 3/32" ground off of them is you use a 1" long screw. The screws that came with the engine are poor quality and will strip out due to not being able to finding a screwdriver that fits them correctly not to mention their dead soft. Doing so will lower the deck height thus raising the compression further. Use Permatex on the backplate making sure the nylon button is in place on the conrod. Ken