I am looking for a Manual for Tecumseh Engine model HM80,Spec 155644V,DOM 02023AD0157,Engine Family 2TPXS.3182BA

Check this chart for valve clearences http://outdoorpowerinfo.com/engine_specs/tecumseh_valve_gaps.asp

You can find a free diagram at www.sepw.com, use the part number of the carburetor as a model number under tecumseh brand lookup. Your carb part number is 640065a.

Try SearsPartsDirect.com if you want to cheaper try your local craigslist

follow link:
http://www.2cpdonline.com/scan_pdf/HMSK80.PDF

40049 is the Tecumseh Part # for a Standard Ring Set, let me know if you need part #'s for OS Rings

Try www.partstree.com you will need to know the model and spec number of the engine. These numbers are either on a sticker on the fan shroud, or stamped into the metal of the shroud...usually near the spark plug.
Good luck.

That does not sound like a complete Tecumseh model number.
You have several options... Your first and probably best option would be your local small engine repair shop. They may even have the parts in stock, if not in stock will likely have it in a few days. Or you can look online at places like outdoordistributors.
No matter where you get the part from you will need a complete model and spec and maybe a serial number ( off of the motor itself). Also be aware that since Tecumseh went out of business a few years ago that certain parts are becoming increasingly hard to find.

plugged carb

try this site its called pats small engines

below is a web site for you to check out the parts at. Hopefully this helps you out. If not, let me know and I will try to get you a better diagram. thanks.

http://www.outdoordistributors.com/pdf/Tecumseh/TECUMSEH-MODEL-HM80-155315N-PARTS-LIST.pdf