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Gas leaking into air filter housing

#1

M

mekelly

I own a Craftsman 28M707 riding mower with a Walbro carburetor.

Gas is leaking into the air filter housing. I removed the carburetor and disassembled it (removed the bowl, main jet, needle, float).

I cleaned it using my ultrasonic cleaner, re-installed on mower. No change, it still leaks.

The float wasn't full of gas so I assumed it was OK and didn't have a crack or hole in it. After reassembly the float moved freely. The needle didn't look damaged.

So I am not sure what to do next. Obviously want to avoid buying a whole new carburetor. So several questions:

- Is it a bad needle seat?
- Could it still be the float?
- What else would cause gas to leak into the air filter housing?
- What else should I do to troubleshoot the issue?

Thanks!


#2

M

mechanic mark

purchase a carburetor rebuild kit & be done with it. 28M707, type XXXXXX, trim XX & code from engine


#3

T

Tinkerer200

mekelly said:
I own a Craftsman 28M707 riding mower with a Walbro carburetor.

Gas is leaking into the air filter housing. I removed the carburetor and disassembled it (removed the bowl, main jet, needle, float).

I cleaned it using my ultrasonic cleaner, re-installed on mower. No change, it still leaks.

The float wasn't full of gas so I assumed it was OK and didn't have a crack or hole in it. After reassembly the float moved freely. The needle didn't look damaged.

So I am not sure what to do next. Obviously want to avoid buying a whole new carburetor. So several questions:

- Is it a bad needle seat?
- Could it still be the float?
- What else would cause gas to leak into the air filter housing?
- What else should I do to troubleshoot the issue?

Thanks!
Click to expand...

After you have done whatever you are going to do, add an in line gas shut off valve and use it when the engine is not running.

Walt Conner


#4

T

tbweng

I have a very similar problem with my mower. Did you find a solution?


#5

M

mekelly

tbweng said:
I have a very similar problem with my mower. Did you find a solution?
Click to expand...

Yes! I replaced the needle seat and the needle. My seat was brass so I had to tap it and pull it out. Very easy to do. The hole in the bottom of the seat was elongated so the needle wouldn't completely seal it off. As long as your float is not cracked and filling with gas, that should fix your problem.

Problem solved!


#6

T

tbweng

mekelly said:
Yes! I replaced the needle seat and the needle. My seat was brass so I had to tap it and pull it out. Very easy to do. The hole in the bottom of the seat was elongated so the needle wouldn't completely seal it off. As long as your float is not cracked and filling with gas, that should fix your problem.

Problem solved!
Click to expand...

I'm glad that fixed your problem!

Unfortunately, I've already tried replacing the needle and needle seat (twice!). Float's not cracked either, so I'm stuck...


#7

B

bertsmobile1

put a tap in the fuel line.
Then assemble the carb without the float bowl.
Hole the float up with your finger then open the fuel tap.
Work the float up & down with your finger and see where the float stops the fuel supply.
If it does not then chances are you have pushed the seat too far into the carb.

I had this happen to me the first time I did one.
I finally ended up seating the seat with the carb in position and checking the float height till I got the seat where the float cut off the fuel when it was parallel to the bottom of the carb.


#8

M

mekelly

bertsmobile1 said:
put a tap in the fuel line.
Then assemble the carb without the float bowl.
Hole the float up with your finger then open the fuel tap.
Work the float up & down with your finger and see where the float stops the fuel supply.
If it does not then chances are you have pushed the seat too far into the carb.

I had this happen to me the first time I did one.
I finally ended up seating the seat with the carb in position and checking the float height till I got the seat where the float cut off the fuel when it was parallel to the bottom of the carb.
Click to expand...

I second what bertsmobile1 said. You probably drove the seat in too far. The other consideration is the float. It's either leaking or not rising enough to seat the needle. Sometimes varnish from old gas will stick on the float pin and prevent the float from moving freely.

The good news is there's really not many things that will cause this; needle, seat, float. One or more is causing your problem.


#9

M

mekelly

mekelly said:
I second what bertsmobile1 said. You probably drove the seat in too far. The other consideration is the float. It's either leaking or not rising enough to seat the needle. Sometimes varnish from old gas will stick on the float pin and prevent the float from moving freely.

The good news is there's really not many things that will cause this; needle, seat, float. One or more is causing your problem.
Click to expand...

If you still want to use the mower now you can install a fuel shut-off valve. Drain the oil (since it likely has gas in it), and fill with clean oil. Use the mower but shut off the fuel valve before turning off the mower. Wait until the engine stops due to fuel starvation. Then there won't be any gas to leak into the air filter and oil.

Turn the valve back on before you start the mower next time.


#10

T

tbweng

mekelly said:
I second what bertsmobile1 said. You probably drove the seat in too far. The other consideration is the float. It's either leaking or not rising enough to seat the needle. Sometimes varnish from old gas will stick on the float pin and prevent the float from moving freely.

The good news is there's really not many things that will cause this; needle, seat, float. One or more is causing your problem.
Click to expand...

Thanks guys! It's very likely that I drove the seat in too far. I'll try backing it off a bit and see what happens. Float and float pin are fine, so must be an issue with the needle seat being to far in from the tip of the needle.


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