What's the difference between a red Briggs and Stratton or Tecumseh engine and a black Briggs and Stratton or Tecumseh engine?
For starters, engines with red shrouds on them mean the engine is an Industrial/Commerical engine (I/C) and has a two year commerical use warranty. (Briggs and Stratton calls their red shrouded engines I/Cs while Tecumseh calls theirs XL/Cs-XtraLife/Commercial.) Either way you put it, the engine is designed for industrial use and is a little stronger than regular black shrouded engines.
Another big difference is that all I/C engines have a cast iron sleeve. These are stronger than aluminum, thus will not wear out as fast. Also, some of these engines utilize ball bearings for PTO (Power Take Off) bearings. These create less friction than standard friction (plain) bearings.
As usual, there is an exception to the rule. Briggs and Stratton happens to put black shrouds on some I/C engines. On these engines there is a decal saying the engine is an I/C.