Small Engines (Lawn Mowers, etc.): B&S Engine will not stay running, hp model, carburator

Question
I recently got my hands on an old Murray Select riding lawnmower, model #465602X8 with a B&S 21 HP model #460707.  I cleaned it up, replaced the spark plugs, fuel and oil.  I have not been able to find an air filter yet, but the one inside looks clean.  I took the manifolds off with the carb, cleaned them and put it bck together.  I am thinking I may have not put the carb linkages back together right, but have no manual to compare it with.  It started but only with the throttle control lever in the choke position, and then died when I moved the throttle to a slower position.  I didn't let it warm up.  Now I can't keep it running.  I also can't find an owners manual anywhere.  When I first turned it over, maggots and water came out of the muffler.  Should it be replaced?  Any help would be appreciated.

Answer
 Hello Patrick:

 Yes I would Replace the Muffler. Also, the Carburator needs to be Cleaned Overnight in Cleaning Solution and Rebuilt. You can View a Complete Breakdown of your Mower at this Addy: http://search.cartserver.com/search/search.cgi?cartid=a-8671&category=MurrayPDF&... and for the Engine at http://www.odref.com/briggsandstratton/model-46/460700-ms1101-0602.pdf Hope this Helps. Let me know what Happens, Please.

 Good Luck

 Respectfully

 John