Old JD

I own a fully restored 1948 JD B and a 1953 JD 40. My son recently asked me a question that I haven’t the faintest idea of how to answer. Why does the 40 idle so slow, getting the full “putt putt affect” whereas the B runs at a much faster pace? Carburation? Camshaft?
Any insight is appreciated.

You should be able to adjust your idle with the idle top screw. You might have to reset your mixture adjustment after doing that. The 2 cylinder JD's that I've owned and been around have all been able to idle at low RPM's unless there is a problem elsewhere in the engine.

A belated thank you for your response. Now to the 40 After bringing it back to life I now have an issue I did not have before when we first got it running. There now is a delayed response when I move the throttle lever from slow to fast or fast to slow. It runs well at either speed, it just takes a few seconds to get there. It almost feels like something is bound up. Of course I have all the sheet metal back on. Could it be a cable or maybe carburetor adjustment? Stumped
Thank you.