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Old April 12th, 2021, 07:04 AM
WE7X WE7X is offline
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Location: Issaquah, Washington
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Default Re: Is it my fuel pump?

But if the problem is the needle in the carb, he should et fuel 'at' the carb when the hose is off the carburetor. He did not.
I am sure I recall mention of small differences here are small differences in the arms on fuel pumps on the 401's and 478's. It had something to do with the effective stroke of the arm. I have not experienced it myself.
Is it possible the fuel pump was replaced and never ran properly after that?...probably not, but I had to ask.
My guess is that the installed stroke is not enough to get fuel up to the carburetor ( maybe one of the check valves in the fuel pump has stuck open) but with a longer stroke (supplied by you), you are getting better pumping action.
Beyond that, I have no other suggestions.
Good luck, and let us know what you ultimately find o be the problem.
Rod J
Issaquah, WA
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