Small Engines (Lawn Mowers, etc.): Snow Blower Tecumseh Q&A, sears craftsman, internal passages

Question
I have a 20 year old Sears Craftsman (tecumseh) 6 hp 3 stage snowblower.    New short block 3 years ago.   Has been running fine, but this year I can't seem to take it off of full choke at all, or it will simply sputter and die.   It also struggles (still on full choke, mind you) while under a load, but MOSTLY when going in the forward direction, regarless of whether it is pushing any snow.   It seems like the act of moving forward just starts to cut off the fuel and/or air supply.   However, it goes in reverse just fine.   Any thoughts?   Help!   Getting buried in Wisconsin.....

Thanks a bunch!

Answer
First off, if you have to have it on choke to keep it running, the carb will need to be cleaned thoroughly.  This includes pushing a piece of tag wire through all of the internal passages and following up with carb cleaner...everything must be spotless.  Then start the mixture adjustment screw on the float bowl at 1 1/2 turns out from lightly seated.  From there, adjust it (either in or out) until it runs smoothly then open it 1/8 turn more.  I can't think of anything mechanical that would cause it to travel in reverse fine and not in forward as the drivetrain is the same except that the friction disc rides on the opposite side of the driven wheel.  It's possible that the carb is crudded up in such a way that fuel sloshes up the stack when the blower moves in reverse (purely a guess).  If you get it running properly (without choke on), you will likely find the drive problem will no longer be there.  If it still is after it is running properly, drop me another line.  Hope this helps.