M38-A1 running bad

[Gary Turman]

My M38-A1 has been running real bad lately. It is hard to start and when it does it smokes a lot for 10 minutes or so and runs bad. Then the smoke will go away and it smooth's out. Next day it starts all over again. I have changed points, condenser, coil, cap and rotor, plugs. Checked valves and they are all working. Rebuilt the carb and changed out the capacitor in the distributor. It's getting good gas flow. I'm thinking carburetor but I rebuilt it, maybe I screwed something up. It's also pinging. Any help thanks...

[markrdje]

The way it smokes,isn't that an indication that the valve seals need replacing?
mark

[Joe Gopan]

By any chance did you misplace the little rectangular brass weight that goes on top of the check ball in the bottom of the float chamber?

[Scoutpilot]

With the engine warm, fire it up and inject a few ounces of Marvel Mystery oil down the carb while holding the throttle 3/4 open. Don't drown it. You may have excess carbon buildup and that will help to burn it off. Then put the remainder of the quart in the gas tank.

[Gary Turman]

Thanks for the help, I did the mystery oil today. Will wait and see. I will check the carb if I have to remove it. I forgot to mention that I can completely take out and in the idle mixture screw without making much a difference on how it runs.

[Scoutpilot]

you should check for a vacuum leak. Ether or propane will work. Start at the front of the intake manifold. Work your way back to the other end. Then starting at the carb studs, work your way around and up the carb. Don't drown it in ether, but use short bursts. An increase in RPM will tell you where a leak is. Pay particular attention to the throttle shaft and bores.