Small Engines (Lawn Mowers, etc.): Lawn mower engine repair, side draft, ring seal

Question
I have a 4 year old, Sears, 6.75 HP, 22 in cut, self-propelled, mulching mower.  I believe it has a Tecumseeh engine, but I am not sure.  It has recently become hard to start after a long (30+ minutes) run.  I have dissassembled the carburator (contrary to my own advice to my kids whom I have told that carburator is a French word for "do NOT touch"!!) and now can't seem to keep gas from leaking out of the large screw (idle mixture?) in the side/bottom of the fuel bowl.  Is there an idle mixture on a small, side-draft carb like this? If so, where? This large diameter screw appears to be the only "knob" to turn.  

Thanks,  Joe  20040612

Answer
Hi Joe,

Congratulations on exploring the unknown.  That's how I learned how things work.  
The large screw is the high speed mixture screw.  Some carbs do not have a low speed mixture screw which is usually located horizontally, on the top of the carb.  If fuel is leaking out of the large screw, then the o-ring seal probably fell off or is damaged.  You can get a replacement at a repair shop or hardware store.  Bring the screw with you.  Hopefully you have solved the hard start problem in the process.

Let me know how you make out.
Michael