sears suburban 15 backfires

[docrocky]

Picked this up at consignment auction and the tractor looks great. Starts right up and blows no smoke but back fires repeatedly even after warm up. Not knowing how long it might have sat, I gave it fresh fuel and added fuel line water absorbent but no change. The drive shaft key looks intact. New plug. Any suggestions? Has a B&S 15 engine.

Went to buy the sears cultivator for my SS 10 and the tractor wasn't even listed on the Auction-zip ad. My SS10 runs ok but I can't solve the fuel drip that comes out of the Tecumseh carb bowl on the bottom.

Thanks