Tractor Repair: Craftsman 20.5 HP tractor with, air filter foam, twin cylinder engine

Question
I have a 7 year old Sears Craftsman tractor with Briggs & Stratton turbo twin cylinder engine. It stopped working and I got a mechanic to look at it. The cylinder connecting rod was broken, which he replaced. Now the engine is running fine when the air filter is open. When the filter and foam protector and placed, the engine stalls. There is excessive spewing of gas upwards through the carburetor. The mechanic  (he is actually a car mechanic friend) does not know what to do. Will apprecaite your advice.

Answer
Jacob Category: Tractor Repair Private: No
 Subject: Craftsman 20.5 HP tractor with Question: I have a 7 year old Sears Craftsman tractor with Briggs & Stratton turbo twin cylinder engine. It stopped working and I got a mechanic to look at it. The cylinder connecting rod was broken, which he replaced. Now the engine is running fine when the air filter is open. When the filter and foam protector and placed, the engine stalls. There is excessive spewing of gas upwards through the carburetor. The mechanic  (he is actually a car mechanic friend) does not know what to do. Will apprecaite your advice.
  
Hi Jacob
Serious stuff if the con rod had to be replaced most unusual hope you were not racing this engine. Just to confirm what I think you are saying is that the engine runs ok when the air filter foam is not in its correct place, and air just flows in to the engine unfiltered, but when the foam filter is placed back in its correct box the engine floods with fuel?  Most unusual first time I have had that one!
Iam thinking along the lines of some thing or some component is not going back as it should – have you changed the foam filter is it the correct one for the machine if it’s the old one does it need cleaning –usually by washing in petrol- but consult the manual for this.
I cant see why it should affect the air filter, but check the float chamber on the carb, is the needle in good shape and does the float bob up and down in the chamber when its full of fuel?
Just as another thought is the engine controls –throttle and chock working correctly when the air filter is installed correctly.
Sorry cant thinks of any thing else at the moment.
Martin