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That D@mned duckbill filter

9K views 11 replies 5 participants last post by  Free-Bird 
#1 ·
The duckbill filter is a tiny inline filter. It is in the fuel line where the fuel line enters the Rack of carbs.




This is the only inline filter between the petcock screens and the Carbs. It can get plugged pretty easily.


See how small and fine it is?



Many folks here have removed it and inserted a more robust inline filter. I used one from an early 80's Honda V65 (cause I had it sitting around in my tool box). Most generic bike shops carry some clear plastic ones that also work well. Another one of those things that needs to be checked if you suspect inadequate fuel delivery.
 
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#2 ·
My previous image hosting is going away, so I am reposting some of these posts that have several images in them.

•____________________________________________________•

The duckbill filter is a tiny inline filter. It is in the fuel line where the fuel line enters the Rack of carbs.




This is the only inline filter between the petcock screens and the Carbs. It can get plugged pretty easily.


See how small and fine it is?



Many folks here have removed it and inserted a more robust inline filter. I used one from an early 80's Honda V65 (cause I had it sitting around in my tool box). Most generic bike shops carry some clear plastic ones that also work well. Another one of those things that needs to be checked if you suspect inadequate fuel delivery.
 
#4 · (Edited)
The hose that connects at that point normally runs up to the tank. I am going to try running it back under the air cleaner, around the frame member, and up to my pingel petcock. Theoretically this will allow me to put a decent sized inline filter there under the air cleaner that will be easily visible. Also I think it better prevents vapor lock because any air bubble has to go up either into the carb or back into the tank (it avoids any possibility of having an "overhead" loop where an air bubble can stick).

Although now that I think of it, it may create an overhead loop right in the carb, just above the needle valve. Well I will try it anyway to see what happens.
 
#7 ·
It is certainly difficult to tell if the air that is visible in the fuel line or filter is air or vapor.

During aggressive right corners when the fuel is low it is definitely possible for air to get into the fuel line. Back in my automotive service days (late '60's and 70's) Vapor Lock was usually cured by insulating the fuel line between the pump and carb, or switching to a rear mounted electric fuel pump.

I don't think our fuel line is in a position to get hot enough to vapor lock, unless the outside temps are extreme.

Any way rerouting like you suggest is understandable and a good idea.
 
#8 ·
I was letting my 99 Thunderbird warm up last week & heard it die as if someone had hit the kill switch, I've checked the petcock and hoses & they check out all the way to the fuel rail. I wasn't able to blow through the line below a previously installed plastic triangle inline that you mentioned but when I took it off the rail, the blockage must have cleared because I was then able to blow through it. Unfortunately when I got everything put back together it still wouldn't start. I once again tried to blow through the line but it's blocked again. Is the plastic inline adequate protection by itself & if so how hard is it pull out the duckbill?
 
#9 ·
duckbill

The filter is located in the carb where the fuel line attaches as long as no one has removed it. when you remove it check it for rust from the tank if it has sat for any length of time with fuel in it. I use an inline filter between the tank and carbs. without any problems. HTH.
 
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