How it Works
The power piston and power jet is used to supply extra fuel when in power mode.
When below power, the vacuum is at it's highest and the vacuum pulls the power piston up, keeping the jet stem up. As the engine gets up to power, the vacuum drops which allows the power piston stem to move down, pushing the power jet stem down, which allows fuel to flow through the power jet.
Removing the Power Piston
Warning! the power piston stem is easily broken.
The power piston is held in the well by staking the edge of the hole.
Start with an awl and scrape around the piston circle to remove excess metal.
Press down on the stem and then let it spring back up. The piston will bang against the staking.
Do this over and over until the Piston comes out.
If the piston is frozen, heat the outside area. This will almost always break it loose. If that doesn't do it, then discard the carburetor as it is probably too corroded.