Small Engines (Lawn Mowers, etc.): B&S 600 series Bogs and stalls, snails pace, responsible advice

Question
I have a new Craftsman mower with a B&S 6.75 600 series engine.  126T05-1070-B1  08060257
The engine starts and seems to run fine.  When you try to cut thicker grass, perhaps cutting 2" high, you have to walk at a snails pace to keep from stalling the engine. I have also tried without using the self propel to reduce load.   The RPMs just drop. Reducing the load, and the engine picks right up again.  There is NO speed adjustment readily available.  I have read that there may be a mechanical governor that should increase the rpms in higher load conditions.  I also wonder if it could be the high speed mixture screw setting.  Just wonder if this engine is as gutless as it seems or if you think something is out of adjustment.  My old 4.5hp has more power than this new mower!
Thanks

Answer
There's an internal governor that should keep the engine speed constant and there could be a problem with this.  It should detect an engine load and open the throttle for more engine speed.

Sears is very picky about their warranties and the only responsible advice I can give you is to take it back and tell them the problem. Trying to correct it yourself will almost certainly void the warranty.  Thanks, PK.