SD-40 Carburetor Breather?

[Krondor]

Hey Guys,

I have an Aisan SD-40 that I am attempting to rebuild. While going through the parts diagram, I noticed that my carb has an additional breather/port that I can not find on any other SD-40.

Here is a picture of the part in question.

The diagram specifies this part as a float chamber plug located in this diagram:

The correct plug should look like this:

Picture courtesy of treerootCO. from the SD-40 thread here:
Aisan SD40 Big Window Carburetor

Does anyone know why it was installed/ What it is used for? Should I remove it and replace it with a brass plug? I am not sure why I would need to vent my float chamber.

Thanks,

Krondor.

 

[thebigredrocker]

I know nothing about SD's. But wouldn't that bolt just drain fuel from the bowl? If so, then the banjo fitting is probably a PO's "improvement". It would allow you to put a hose on that nipple when draining.

 

[Krondor]

The bolt is used for draining fuel from the bowl. Can you think of a reason why the PO would want to have easy access to drain the fuel? I wouldn't think that you would want to drain fuel from the carb very often if ever...

 

[thebigredrocker]

Perhaps was having an issue with fuel contamination. Or liked to swap jets often.

 

[shawnfj40]

Who knows unless he was trying to have a quick way to tell if the float needed adjusted?