I bought it used it seemed OK,but now I have loss of power.I NOW have a brand new battery.What can I do to the engine or carburator to fix problem?How do I properly adjust carb?Should I overhaul the engine?I haven't found a rebuild kit for my B&S engine(14.5) Any help would be great.Somone told me that I should clean off the top of the piston(remove carbon deposits) should I?

No need to overhaul the entire engine, and the carb is unadjustable... (epa, thanks >:(

DO YOU have a small engine shop around... they should have a rebuild kit for it, briggs still supports very old engines to new.
The piston cleaning? Naa, that would cause hard starting.

No adjustments on carb? I didn't see any adjustment screws,I thought they would be hidden or internal or something. So all I can do is to clean the carb,change plug, and air filter? Does a non adjustment carb go bad? And what is deal on the speed limitation shouldn't 200cc's be able to go faster,especially when the blades are disengaged? It is a 6 speed. Any more info on this mower/engine? Thanks Briggsdude on your info,there is a small engine shop near me. But I am reluctant to visit. I was there before and they sell go carts mainly,HIGH END stuff.Is there an ONline store that You can recommend to me? I was on B&S.com and I din't see a kit for my motor. Most kits were around $100 is this the going price? A new engine costs nearly $800,and A new mower is only $1500 or so depending.Should I buy a new carb? Do they make adjustable replacements?

No a carb doesn't go bad... and no there are no adjustable replacements.. (jackssmallengines.com comes to mind for a place to order)
As for the speed limitation... these engines are designed to run at 3,600 rpm for hours upon hours... any more and you over stress the internals.
Now ground speed... swap for a bigger pulley up front on the engine, smaller on the trans.