Triumph Repair: Stromberg 175 cd- Triumph Vitesse, piston movement, worn surfaces

Question
I have recently purchased a 1968 mk1 2litre Triumph Vitesse with Twin stromberg 175cd carbs. With no oil in dashpot lifting the piston/air valve with my finger is an easy task. But when oil put in dashpot, piston will be difficult to lift! I have an idea that the oil is seaping down between worn surfaces and its hydraulicing. Is this a posibilty, do I need a new carb cover and piston/air valve. Any help much appreciated!!

Answer
Hi Chris,
If you over fill the top with oil,(engine oil) the piston will be hard to lift the first time but it will usually push the excess oil out of a small hole in the plastic cap. Even when the oil level is correct you will have to lift firmly to lift the piston because that is what the oil is in there for. Not as a lube but as a shock to prevent the piston from moving up too quickly. It dampens the piston movement at idle due to pulses and it holds the piston down when you open the throttle quickly. This speeds up the air across the jet which adds extra fuel. This takes the place of an acceleration pump on a conventional carburetor.
Howard