Reply To: Mercury K1? Or maybe not?

[John]

Actually, that “carb” is a bit more than a simple air/fuel mixing valve. It contains a spring loaded poppet valve that opens and closes with each stroke of the piston. You will note that your motor does not have any reed valves. The poppet performs this function. When the piston moves down in the cylinder, it pressurizes the crankcase, and forces the poppet closed. On the piston’s up stroke, the resulting vacuum in the crankcase lifts the poppet off its seat, allowing air (which mixes with fuel metered by the needle valve) into the crankcase and allowing fuel past the needle valve. You will see that the opening for the needle valve is in the beveled seat for the poppet so that a closed poppet also stops fuel flow. You will be able to hear the poppet clanking on the seat, while the motor is running. These contraptions work surprisingly well.My 1941 Sea King with poppet starts easily and runs smooth. However, you won’t win any races with that motor. You will probably find that you need to adjust the needle valve for best operation as you move from idle to high speed operation, and vice versa, as there is no separate idle circuit.

Kirk’s picture of the bottom of the valve shows a pin and screen. These also perform a function. To start a cold engine, push up momentarily on the pin, which lifts the poppet and allows a bit of fuel to flow past the needle. This fuel will wet the screen, acting to enrich the fuel/air mix and thus prime for cold starting, since there is no choke on these motors, either.

John Van