Engine cub cadet 125 1970

[kknngg]

Just got my mower running again, dirty card and fuel. My problem is when I throttle up and engage mower deck, 42 in, the tractor is back firing consistently, I put in a new plug but can't seem to get it to stop back firing while running at medium rpms. Do i need to adjust throttle setting or fuel

 

[mechanic mark]

http://service.mtdproducts.com/Training_Education/IH-GSS-1464/IH-GSS-1464.pdf information

http://www.briggsandstratton.com/us/en/support/faqs/engine-backfire-afterfire Post all numbers from engine, thanks.