Petcock fuel filter screen

[mike-stroz]

I was running my KA-38 the other day and it seemed to be leaking gas when it was stopped, and it turned out to be a leaky petcock. I replaced it and now it shuts off the fuel, but the new one doesn’t have a screen on it. How hard is it to put a new one on or are there any alternatives to soldering a new screen on? I’m awful at soldering because of my shaky hands so I’d like to avoid it if I can.

[Buccaneer]

You could install an "in-line" filter but it’s not going to original.
I’ve made several petcock screens using 100 mesh brass screen.
Not hard, just takes a little time and practice.
I drill out the old solder and chunks of screen so
I have a nice surface to solder in the new screen.
I form a piece of screen around a drill bit a size or two
smaller than the hole in the petcock, and size the screen
so the edges overlap about 1/8".
I then coat the edges with paste soldering flux, and pre-tin
both edges with my electric soldering gun.
I use the drill bit in a vice to hold the screen while working on it.
After tinned, I overlap the edges and soldering it together.
I then cut a little round piece of screen to go on the one end,
and solder it in place.
Then I put the screen in the petcock with a little flux, and
use my propane bottle torch to heat the petcock enough
to melt the solder, holding the screen in place.
Only use enough solder to get a little bead around the
screen….. if too much gets sucked in the petcock,
it might plug it up!

Prepare to be boarded!

[amuller]

Where do you get the 100 mesh brass screen? I’m sure it goes much better with shiny new screen than old tarnished/oxidized stuff.

[frankr]

I have used the 100 x 100 on several motors and have advised others to do likewise. However I’ve had some that have given me a hard to diagnose problem. It seemed to not want to start the initial flow but would be ok once the gas was flowing through it. Anyhow, I’ve since abandoned the 100 x 100 x .006" holes and am now using 80 x 80 x .007" holes and it seems to be much better. I get it from mcmaster.com I’ve also experimented with a drop or two of Locktite thread locker to hold the roll in the fitting instead of solder. Rinse out any that doesn’t cure. If you overlap the edges a bit, it really doesn’t need solder at the seam. Worked for me.

[amuller]

My experience with tractors and such is that an inline filter isn’t an adequate substitute for some sort of screen or standpipe in the tank, because a bit of leaf, or whatever, can float over the opening and shut things down. Can be a hard-to-track-down cause of fuel starvation. Guess how I know this. "Course, marine tanks seldom tap the fuel off the bottom, but the principle applies, IMHO. Fairly coarse screen in the tank, some sort of inline filter or sediment bowl to catch the water and fine stuff. This is what airplanes use, at least in my limited experience. I was just looking at (throwing out) an old plastic outboard tank. The inlet screen was fine mesh, across the diameter of the pickup tube, not extended at all. POS design for sure.
When making a screen, no need for a round end cover unless you care what it looks like. Just make it 1/4 longer, pinch it flat, fold it over…helps hold everything together.

[Tom]

Doesn’t that motor have a round screen at the bottom of the carburetor where that big nut attaches the fuel line?

T

[mike-stroz]

quote Tom Manley:

Doesn’t that motor have a round screen at the bottom of the carburetor where that big nut attaches the fuel line?

T

Yes it does, but like was said, it’s also good to have a screen in the tank to keep debris from plugging up the line.
I’ll get some of that screen from mcmaster carr and try my hand at soldering it in

[Author]

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