I have a 5hp, B&S, Craftsman rototiller that starts easy, but the engine runs rich and it misses. A couple weeks ago I cleaned the carb because I had some old gas in it. It ran really good for a couple day, and then I couldn't start it. I took the carb apart a second time, put it back together and now it starts easy, but it misses and runs rich. There is no difference when I take the air filter off. I thought maybe it was dirty and causing it to run rich. The carb is the type that sits above the gas tank. Any suggestion would be appreciated.
Thanks

A leaking fuel pump diaphragm or a faulty fuel cap can produce those symptoms.

is there an adjusment screw?

It would seem to me that if the fuel pump diaphragm was leaking it wouldn't pump gas into the reservoir that supplies gas via the main jet to the carb?

There is a screw on the side of the carb, but it doesn't appear to be an adjustment screw. There is no spring to hold it in place if you loosened the screw. I will give it a try anyway. Before I cleaned the carb it was screwed all the way in. After it was cleaned it I put it back in the same way.

A small tear or distortion in the diaphram can allow fuel to leak around it while still allowing it to pump fuel. Try running it without the fuel cap and see if that makes any difference.

I ran it with the gas cap off. It didn't make any difference. It still ran rich and missed.

I put in a new diaphragm. It runs better, but still misses and the governor hunts. I have a feeling that there must be something clogging up the carb. The diaphragm was definitely in need of replacement. Any suggestions?
Thanks

Possibly a leaking gasket between the engine block and carburetor....

I read somewhere that if you spray carb cleaner around the in take gaskets while the engine is running there will be a change in the rpm if there is a leak. I will give it a try and see what happens. I also have some Fast Start in a aerosol can which I could use, but I think it would be safer to use the carb cleaner. Thanks for the suggestion.

I rechecked the carb and found that the pilot jet was clogged. The engine ran much better when I replaced it. It was still missing a little, and so I replaced the spark plug. It now seems to be running like new. To recap what I did: I replaced the diaphragm per 30yearTech suggestion, clean the carb including the pilot jet and replaced the spark plug. BTW squirting around the carb with carb cleaner trying to detect a gasket leak while it was running didn't do anything other than clean the outside of the carb.
Thanks for the help.