If you need to reuse the old gasket, a touch of sealant like high tack or some shellac based stuff can get you through if need be. Too much can cause problems! To avoid tearing when removing, a razor blade/ exacto knife can help. IE if the gasket for the most part is stuck to one side, use the knife to remove it from the other. If you are working on a unit w/ plastic surfaces, be extra careful not to harm the surface. Replace the gasket if you can.

Must: As Tom has recommended proper Gasket Sealant or Dressing such as Loctite or Permatex , Mr Gasket Sealing Compound for the use intended are the Best . I also sometimes use a worn out Hacksaw Blade sharpened with a grinder along the former tooth area to use for such gasket removals .

Thanks guys. I had a feeling that something existed that I could use to get a good seal and prevent air leaks. Now I know what to look for.

FYI, I just finished my second successful rebuild of a 4 cycle carb. Most of the credit goes to this forum and the answers I have received over the past year. This time it was my neighbors Toro snowthrower. He had borrowed mine for the past 3 years. I actually never knew he had one buried in the back of the garage until he told me. I drained the fuel, replace the fuel line, added a shutoff valve, and rebuilt the carb. Total $28 in parts and all is working again.

I too, am very happy with my last Tecumseh carb re-build. It was the first time I removed the welch plugs and cleaned out the passages behind them. I used a piece of 24 gauge solid copper wire. I had torn the carb down a few times before but it never ran right until this time. The old 5 hoss just purrs and starts very easily.

In the "you can always learn something new" department, I never knew what those "plugs" on carburetors were called. Now I know. The company is still in business by the way.
A little history;
http://www.britishcarweek.org/welch_plug.html

Can I just use permatex without a gasket? It works on car valve covers. What about using it instead of the o-ring on the bowl?

Putting it on the curb with a free sign would be a better idea. Buy the bowl gasket should it need one.

Ok, ok...those gaskets are darned expensive. May try to cut my own from sheet gasket material.