Small Engines (Lawn Mowers, etc.): Tecumseh 8hp backfires, repair experience, mechanical ability

Question
Today i purchased a 30" Murray model # 30544x92d riding mower with 8hp tecumseh engine (model # TVM195 150263d).  At sellers house everything worked great simple choked engine for a second and it started fine and ran fine at high throttle.  Loaded in my pickup brought it home and it now backfires really bad at high throttle but runs smooth at lowest throttle.  I can move it to low throttle and very very slowly idle it up to high throttle and it will accelerate and run okay for a second or two then start backfiring again and produce black smoke from muffler and the engine "cycles" up and down.  Is it possible that something vibrated out of adjustment on the ride home.  I have zero small engine knowledge so please be as detailed as possible. I do have a high mechanical ability and can follow your direction just no small engine repair experience.

Answer
 Hello Aaron:

 The Trip May have Stirred Up Trash in the Carburetor Bowl and the Carburetor May need to be Cleaned. Lightly Tap on the Carburetor Bowl. The Float May be Sticking Also. If it is the Tapping on the Bowl May Jar it Free. You can View a Breakdown/IPL at this Addy http://www.outdoordistributors.com/ and Select the T. Then Select Tecumseh. Then Select Don't have Part Numbers. Then Enter the Model Numbers TVM195-150263D and Click Go. A Good Site for you will also be this 1; http://www.tecumsehpower.com/CustomerService/BSI.pdf Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John