Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Hello, sounds like it could be an air leak.Is there any play at the crank ends? Are the oil seals wet? Is the fuel filter connected?. maybe try to adjust the carb,open the low speed 1/2 turn. A special tool is need but you may be able to make one. You can try tapping a piece of 3/16 copper tubing onto the screw.
Also, the carb adapter could be loose or cracked. if loose the gasket could be torn.
Did you permatex the gasket before or after new carb was installed?
open both screws a 1/2 turn or more on the new carb to see if any difference. Did you check for crank wobble and wet seals? Are the 4 screws that hold cyl to c/case tight ?