So thats the issue. I've got a lawn tractor with a Briggs 14 hp ohv engine. It starts and runs fine with plenty of power but only if the choke is about halfway out all the time. I've changed the plug and installed new air filter. I pulled the carb, completely dissassembled it, and soaked it one of those paint cans of cleaner but no change. The only thing I haven't done is adjust the valve clearance as I don't have a spec manual. There is a small bit of clearance between the valve and rocker though. I'm at a loss. Any ideas? Edit: tried re-tuning the mix. Richening nor leaning had any effect. It ran the best the way I found it. Edit2: We bought the tractor used. It didn't appear to be very well maintained which prompted the general tune up. Engine runs exactly the same as before I touched it, maybe a bit better minus the choke issue. When I began playing with mix, I wrote down the exact number of turns it was already out so I could return it to it's original position. Float was clean and moving freely. Didn't have a filter to begin with (it does now though) which is why I pulled the card and cleaned to begin with. Gaskets were in good shape and everything was reassembled perfectly(I double checked twice). This isn't the first small engine I've worked on btw. I've been rebuilding them for about 10 years. This one just has me baffled. I'll check the muffler once it warms up a bit outside. Thanks for the suggestions. If nothing else, it's confirming that I haven't missed anything (except whats causing the problem of course).