I have a 18.5hp briggs opposed cylinder engine. It has started using about twice as much gas to mow. The airfilter is clean when you run it full throttle it seems to flood some and run rough and has lost power and it smokes a little black smoke. But when you run it at an idle or about half throttle it seems to run good. It starts easy. I have cleaned the carb 4 or 5 times and tried adjusting the float so it doesn't get as much gas in the carb and I have put a complete kit in the carb it included new gaskets for the carb and gaskets and diaphram for the fuel pump a new needle and seat and adjustment screw I replaced all of this and even if I shut the adjustment screw all the way it still runs all of this has helped a little but it still has the same basic problem just a little more power and seems to run just a little bit smoother at full throttle but still not as smooth as it should be and when you put it under a little load it almost stalls the engine it has good fire and compression and the problem started all at once. The model # is 42a707 the type # is 1238-01 and the code # is 9705125a any help would be greatly appreciated

Hi,
Despite the fact that you say the compression is good, I would say you have a partially blown head gasket. The use of excess fuel and almost stalling seem to tell me this.
Peace,
Clarke