I've been having a problemgetting my old 45flathead to consistently run good. I found rust in the fuel tank so cleaned & Kreemed it. Replaced the fuel filter & thoroughly cleaned the carb with carb spray cleaner. It runs a whole lot better but still occationally will spit & sputter under excelleration like it's starving for fuel. I have to stress the fact it does not do this all the time. I've tried adjusting the high speed but it doesn't seem to help a whole lot. I pulled the plugs and they are fairly black so it's not lean and the intake is very well sealed so no air leaks here. I've not inspected the points but will and put in new plugs again asap.

It is a 1965 flattie with a Linkard(?) carb.

Anybody got any ideas on what might be the cause?

 

Since the Linkert is a simple straight tube carb, it doesn't take well to quick throttle operation. Try easing the throttle open and see if the problem goes away.

 

I finally had some time and took a look at the points. Gap was way to wide and they need replaced. I cleaned them up some and regapped them just to see if it made a difference and it certainly did. The ol' girl putts along just fine & rarely miss fires at all.