Carb Still Leaking After Parts Replacement

[Sinfahl]

Engine model:123K02-0193-E1

Primer button type carb

I've replaced the float, needle valve, and the needle valve seat using all B&S genuine parts. From bench testing everything looks great; I test that everything seals right on the bench by turning the carb upside down and drawing a 5psi vacuum on the fuel inlet and it holds steady.

After this, I start to notice problems

1) The float doesn't sit level, no matter how far I push the seat down beforehand. It's not overly tilted like "\", but it is clearly noticeable

2)I can reinstall everything to the lawnmower and run it a few minutes and there's no leaks, but when I come back maybe an hour later the mower won't start and I start to get a steady stream of fuel leaking out the gold tube that sprays fuel after priming

3) The stream of fuel from the tube leaks worse when the gas cap is removed

 

[Tiger Small Engine]

Engine model:123K02-0193-E1

Primer button type carb

I've replaced the float, needle valve, and the needle valve seat using all B&S genuine parts. From bench testing everything looks great; I test that everything seals right on the bench by turning the carb upside down and drawing a 5psi vacuum on the fuel inlet and it holds steady.

After this, I start to notice problems

1) The float doesn't sit level, no matter how far I push the seat down beforehand. It's not overly tilted like "\", but it is clearly noticeable

2)I can reinstall everything to the lawnmower and run it a few minutes and there's no leaks, but when I come back maybe an hour later the mower won't start and I start to get a steady stream of fuel leaking out the gold tube that sprays fuel after priming

3) The stream of fuel from the tube leaks worse when the gas cap is removed

Buy another carburetor.

 

[Sinfahl]

Buy another carburetor.

So I guess they just get to a point where they'll just act up no matter what? This isn't an aftermarket carb.

 

[ILENGINE]

Was the donut valve seat installed correctly and not upside down, which can cause a different float height. Also was there carb cleaner residue in the carb when the seat was installed. Carb cleaner will make the seat swell and in some cases crumble. I am not a fan of using vacuum to check a float seat. You can create a vacuum in places were the same component won't hold pressure.

 

[StarTech]

Engine model:123K02-0193-E1

Primer button type carb

I've replaced the float, needle valve, and the needle valve seat using all B&S genuine parts. From bench testing everything looks great; I test that everything seals right on the bench by turning the carb upside down and drawing a 5psi vacuum on the fuel inlet and it holds steady.

First you don't Draw (pull) a vacuum as that just makes things seal even tighter. You pressurize at 7-10 psi (usually around 7 psi) and see if there any loss of pressure. If it going to leak it leak under pressure this what pushes the needle off seat even under flow systems. This pressure test needs to done for at least 30 minutes.

If pressure loss it can sometime be leaking around the needle seat and not where the needle meet the seat. And seems to be some defective after market seats out there this year as I done ran into a couple.

 

[Sinfahl]

Was the donut valve seat installed correctly and not upside down, which can cause a different float height. Also was there carb cleaner residue in the carb when the seat was installed.

I installed the valve seat with the ridged side facing the carb and the flat side facing the needle.

First you don't Draw (pull) a vacuum as that just makes things seal even tighter. You pressurize at 7-10 psi (usually around 7 psi) and see if there any loss of pressure. If it going to leak it leak under pressure this what pushes the needle off seat even under flow systems. This pressure test needs to done for at least 30 minutes.

If pressure loss it can sometime be leaking around the needle seat and not where the needle meet the seat. And seems to be some defective after market seats out there this year as I done ran into a couple.

Ohh I didn't know that was the distinction when testing. I wish there was more written about this.

I did use an oem seat & needle however.

 

[Sinfahl]

Here's a highly magnified pic of the seat if it helps any.

 

[slomo]

Looks like a beaver has gotten to it.

.

 

[Rivets]

In my opinion that seat is toast and should be replaced.

 

[grumpyunk]

You could try several things to help sealing. A cotton swab(Q-tip) dipped in valve grinding compound and twirled around while held against the seat may polish the rough edge enough to allow a good seal. You could attempt to remove the seat and flip it end for end and re-install it. The other end may have a cleaner edge.
You could try using a drill bit, operating by hand, to skim of a thin edge of the seat to produce a smoother area for the needle to seal agains.
Finally, a new seat...
When testing, invert the carburetor, and blow through a length of fuel line attempting to blow air past the seat. If you can't blow air past the seat, l liquid fuel would have a harder time getting past. The weight of the float should be enough to produce a decent seal.
It is possible the needle did not poke into the seal enough to allow the float to sit parallel to the gasket surface. It might sit better when introduced to the other end of the seat surface. The float 'tang' that pushes on the non-pointy end of the needle may be bent using heat if you cannot get the float to sit level. It should not be required if you have good proper parts.
tom