Not sure what you mean about it running weak, that could be anything from a dirty carb or worn out spark plug to needing a full engine overhaul., Your machine is in much better condition than my 1980 Horse. Mine has the 7 HP Kohler with manual start. MTD carries a lot of the parts for these http://www.troybilt.com/webapp/wcs/...reId=10001&catalogId=14102&categoryId=1211102