Small Engines (Lawn Mowers, etc.): 9hp Tecumseh Snow King overheating, craftsman snowblower, adjustment screw

Question
Mr. Jones, I have a year 2000, 9hp Craftsman snowblower with a 9hp Tecumseh Snow King engine. (Craftsman snowblower model number 247.888530)(The --carb part number-- in the Craftsman owner's manual part list is --part number 640052--.
I have a good mech. background but need assistance with the following.

During the first few years of operation I drained the gas during summer storage. On subsequent winter runs to the present, the engine would "hunt" or surge at idle ""and"" at high speed. I used a product called Sea Foam engine treatment that cured (most) of the hunting/surging. ((Note: 2 years ago, I removed the float bowl cover and carefully adjusted the float to move just a bit higher inside the bowl in hopes of enriching the mixture - I also sprayed carb cleaner in all passages I could find - no help)).
As the suspected internal carb varnish cleared, the engine ran better, but seemed to --continue--to run so lean that I operate it with one notch of choke on all the time. If I fully turn off the choke, the eng. hunts/surges, and/or sputters a bit.

ALSO, to prove that the carb runs so lean, the eng. seems to overheat by slowing down on it's own after approx. 30-45 minutes of hard running.  I immediately reduce the throttle to idle to let it cool off a bit. This eve. 1/3/06, as I cleared the heavy New England snow, I noticed the muffler glowing orange through it's exhaust holes.

I am obviously concerned about burning the eng. out!!  

My main requests/questions:

1) IS THERE A WAY TO ADJUST, MODIFY, OR REPAIR THE CARB TO ENRICHEN THE MIXTURE. (There does not seem to be any mixture adjustment screw on the carb!!)

2) --OR-- Should I just purchase a whole new carb?

Thanks in advance for your response!
--Steve--

Answer
Unfortunately there is no way to adjust those carbs.  Cleaning with compressed air will usually fix the lean problem but some of those carbs have an internal check valve that sometimes sticks.

You can soak the carb in some Berryman carb cleaner that comes in a one gallon container.  You will have to remove and replace the inlet needle seat because the carb cleaner will dissolve the old seat.  Make sure to remove all plastic carb parts because the carb cleaner is so strong it will dissolve them.

When replacing the inlet needle seat install it GROOVE side DOWN.

Once in a while we have to replace carbs but soaking them will usually cure the problems.

Make sure you check the headbolt torque, 200 inch pounds, and the intake gaskets to ensure there are no air leaks.

If you decide to replace the carb be prepared to spend some money...I'm still amazed why these little carbs cost more than automobile carbs.

Let me know if soaking and compressed air fixes the carb.
Eric