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1956 TR3 carburetor problem

Mike Weikert

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The number 2 piston on my SU carburetor will not move up and down when engine is being accelerated. When the engine is not running the number 2 piston will not move all the way to the bottom when it is raised by hand. I have switched the piston, spring, and camber from position 1 to position 2 but I get the same results. Everything works fine on number 1 but number 2 does the same thing. I also cleaned all of the parts with carburetor cleaner.
 
As I recall, the jet has to be centred around the needle in the piston. The piston should fall with a small thud when the piston is raised and released.
 
Further to the above: Loosen the brass jet in the body of the carburetor, shift the jet around slightly until the raised piston, when released, falls all the way, with the “ thud”, when released. I hope I’m addressing your problem.
 
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