I've recently got my 53 running after sitting for over 20 years. its idling really smooth, the problem occurs when i give the throttle a lil rap, it coughs and stutters and almost dies. if i give it a lil more throttle the problem goes away. Im convinced the vacuum advance is not actuating properly, does that like the symptoms?
You can see the advance move the dist. if it's working. The leather acc. pump in the carb is dry & shrunk. Clean the carb. I'd start by tuning it - comp. test, adjust the valves, etc.
Agree that sounds like the "pump shot" isn't enough. Not vac advance related. With engine OFF look down throat of carb and watch for a stream of fuel in each barrel when throttle is actuated. This prevents a "bog" or hesitation on acceleration.
rebuilt carb? sounds like accelerator pump is dry and not shooting enough to remove the off idle stumble. remove acc pump, if its a leather skirt, soak in motor oil for a while it will soak up and swell and work again....sometimes. if its rubber, replace it.
all good suggestions. Check your timing and since the carb was recently rebuilt make sure you have the right gasket. pic from HAMB archives
when i rebuilt the carb i put a new bakelite insulator on it with the slot for the vacuum and i cut my own gaskets with the opening. i checked the timing a month ago its either 6 or 9 degrees advanced i cant remember what one.
If you have a spare condenser throw it on. I struggled pinning down a stumble, a new condensor fixed the problem after trying just about everything else. Good luck. Cesar
Yes, I also think it may be a lean condition , I my case the vacuum canister diaphragm was torn and leaking. .. so the advance didnt keep up and it was running leaner than it should...just my 2 cents. ..
Try to choke it a bit. Pinch down on the choke and see if it still does it. If that stops the problem maybe a bigger pump shot. Had a similar problem. Idle being too low can also hurt.
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