Pulsa Jet Question

[Mek-a-nik]

130202-0685-01-76111807 Briggs mentioned on the "Rusty Tank" thread.
I cleaned the carb and used new gaskets and fuel pump diaphragm.
It leaked between the carb and tank. I flattened the bottom of the carb and used 2 gaskets. The leaking stopped.
It runs good, but right after shutdown, gas is somehow pulled into the throat of the carb and it leaks out of the choke slide. It doesn't last long. What's doing this?

[bobodu]

The only thing I can think of is pressure in the tank.Loosen the cap.

[bgsengine]

Most likely missing the swirly strip of metal that was inserted in the carburetor throat (between engine and throttle) - they used that to increase air turbulence and improve atomization of the fuel.

Engines missing that part where they were originally equipped, usually will have that same problem - fuel condenses and puddles.- the carburetor gets adjusted richer to compensate for the amount of fuel that is not being fully atomized and drawn in to the engine.

It was not uncommon to see some "wannabe" DIY mechanic that thought the metal strip served no purpose, and yanked it out.. or removed it and forgot to put it back in.. one told me they thought it was gonna get sucked in and ruin the valves.

They discontinued adding that as the carburetor design changed and improved, they no longer needed that swirl port strip... but older engines, unless carrying an updated carburetor, usually had them, so if it was not noted (or it could have been missing for years) it could be assumed that there's nothing missing..

How that works is it's like wind blowing across a lake - water (puddled,condensed fuel) may pile up on one end but not quite be blown all the way into the air, once the wind stops, the water (fuel) flows back to find its "level"

[Mek-a-nik]

Brian, thank you for your detailed explanation of the spiral. I knew some had them because of the fuel distribution, but I didn't know which ones. This one is still there.

Bo, you nailed it. I loosened the cap and it went lean. Some kind of pressure going on there. I never considered the cap as an issue because I was thinking it would starve for gas, as it would with a float carb. Obviously, Pulsa Jets is different!

Thanks fellas.