Topic: Engine shuttering while at idle

[triple nickel]

 22r  Had a problem getting fuel to the carb had to pump peddle many times. Put a new Accelerator Pump Diaphragm and that solved the problem. Now when I start it up running at idle it sounds like the motor is misfiring and shuttering  just at idle. Needed tune up so replaced plugs rotor and cap set timing with no change in the shuttering. When I was adjusting the fuel air ratio the adjustment screw has no effect on the operation of the motor. I can tighten the screw all the way in and out with no change in engine operation. I have checked all of the vacuum lines no leaks. Reset timing again no help. The engine has 320,000 on it I have never replace the carb but never had a problem other that the accelerator pump diaphragm. Does it look like it is time for a new carb?

[Osage1978]

Any backfiring at all & have you held a dollar to the exhaust. To me it's reminiscent of a stuck or burnt valve. Hope I'm wrong but I'd rule it out if it were me.

As for a new carb, forwhat it's worth I have a weber 32/36 on my 22r & am super happy with it. Runs excellent, great cold start, lots of power & great milage. No complaints

[someirishjerk]

I'd spray a bit of carb cleaner around the intake manifold and see if the engine speeds up or surges. Rule out a bad gasket causing an intake leak. Maybe check your valve adjustment, too.