wheelhorse 520-H engine trouble

have spark. fuel, compression but will not start. looking for suggestions. the rotor and the ignition module are new. didn't have good spark before but now the spark is nice and blue. can not see any way to time it other than the key on the crankshaft which turns the rotor, but it acts like it is out of time because it will backfire out the carb. every once in a while it is an onan engine P220G-I 10955. don't know what else to do with it. oh- and the gas is new and the plugs are new. HELLLPP

Will the engine fire if you spray carb cleaner into the carb air horn? If it does this will mean you probably have a fuel delivery problem. This manual may be of some help to you. https://www.mytractorforum.com/images/reference/Onan_16_18_20_24.pdf