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73 Johnson 20hp runs rough and slight backfire

R

rohan2

Member
First of all, I would like to thank all for the info to get me this far. After replacing the coils on my 20hp Johnson and cleaning the carb. It will crank..AT LAST!! But,.. It runs very rough. And has a slight backfire. The motor shakes(worse than normal,lol) when running. I also see I need to replace the water pump. Any ideas on what I should check out or adjust. The only adjustment I see on the carb that I see is a big needle valve that connects via linkage to my rich mixture. I was happy to have it crank, and am looking forward to going on the river. Also for the water pump. there is a small plate about halfway up the foot. When I remove it, it looks like my shifting rod linkage. If i remove the screws and remove the bolts on the foot. Will i be able to remove the foot then to replace the water pump?
Thank you for any all help..
Don
 
UPDATE: changed water pump. Now sprays plenty of water out of the exhaust. I can put my hand on the motor after running. Hot, but not to hot. I also noticed the motor runs a lot smoother half choked. I took the linkage off the mixture screw, and adjusted the top valve. Made no differance. WTheck..
 
When you cleaned the carburetor did you remove the orifice ( high speed jet ) that is found in the bottom of the carburetor bowl ?It and the passage way to the side must be clean !----------This is often a step that is missed and leads to all kinds of running problems.Having to use the choke clearly indicates a fuel blockage in the carburetor.
 
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cleaned the orifice. made a little difference. I can pull the choke to make it idle fairly smooth.BUt have to adjust choke to rev up. Will try the adjustment mentioned Kim. ty for all input.
 
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