Small Engines (Lawn Mowers, etc.): Onan B43M misfire (Case 446 garden tractor), case 446 garden tractor, intake manifold gasket

Question
Hello.  My Case lawnmower has a 16hp Onan engine on it.  The mower ran fine this spring but now it developed a severe misfire and usually only runs on one cylinder.   If I choke the motor it seems to run on both cylinders but it has no power and at idle it will die.  Last summer I replaced the styrofoam float with a factory replacement brass one due to the other one becoming saturated with gas and not floating.  I double checked the mixture screws and they are 1 turn out on the idle screw and 1 1/4 turn out on main needle screw.  I also removed the carb and cleaned it.  Compression in the cylinders is 92 and 96 psi.  The mower had new points on it 2 years ago, but I replaced them again and installed a point saver on it which made no change in the way the motor ran. (http://www.kirkengines.com/)  I tried adjusting the points gap in and out and that did not help either.  Do you have any suggestions.  Thanks, Jeff

Answer
  My experience with Onan is quite limited, as I usually just work on homeowner lawnmowers, but had a similar running problem once, turned out to be a leaking intake manifold gasket, which was discovered with a carb spray, hard choking would let the one side run half=assed, etc.
The leak was so bad it starved the one side and it wouldn't hit,
and it was an Onan.

Other than that, I have not much time with Onans, hope you understand....

Thanks.