Topic: CB550 Carburetor Fuel Line Plugged

[roberhow]

Greetings,
I have a 1976 CB550 with Keihin carburetors. The fuel line that feeds carburetors 3 and 4 is restricted causing limited flow to carb 4. I have filled the line with carb cleaner. This fills float bowl 3 and maybe 25% of float bowl 4. They have recently been kitted, and everything looks clean inside. It appears there is a restriction between the "T" junction and carburetor 4, just my best guess. Looks completely inaccessible... any experience with this would be greatly appreciated. 

[Bankerdanny]

The restriction is in the line that connects the two carbs, not the line that brings fuel from the tank. You can separate the carbs to clean or replace the connection. It's a pain in the ass to get the older carbs apart, but it can be done. Just take your time and take lots of pictures during the process so that you have a clear record of how to put everything back together.

[Deltarider]

First I would simply blow air through the #4 float valve opening upwards after you've removed float and float needle*. Can be done with compressed air or even a bicycle pump. No need to separate carbs.
* Now that you're at it you can inspect valve and needle and maybe polish them very lightly, veeeerry lightly.

[Scott S]

 Are you sure it's not the float height of #4 that's the problem?

[Deltarider]

Are you sure it's not the float height of #4 that's the problem?

That would make sense, Scott. If it gets filled for 25%, at least fuel gets true. For the moment forget what I wrote before for later and save it for later.

They have recently been kitted

Could you be a bit more specific? Have you been 'adjusting' the float? Did you happen to use aftermarket parts?

[flybox1]

What about the atmospheric vent preventing #4 from filling/equalizing as fast as the rest?

[alacrity]

and if you DO pull the rack apart, make sure you have all the right size o-rings to put it back together...

[roberhow]

The number 4 float has been adjusted and even with floats 1,2 and 3. When I blow(just with my mouth) through the fuel line into carb's 1 and 2 it's much easier than with 3 and 4.

[Deltarider]

The number 4 float has been adjusted and even with floats 1,2 and 3.

You didn't answer my question about aftermarket parts. After you readjusted float #4, does #4 still fill insufficient?

When I blow(just with my mouth) through the fuel line into carb's 1 and 2 it's much easier than with 3 and 4.

Then check vent 3+4 first. If there really is a blockage in fuel line 3+4, I'd use my rubber airpump (to inflate rubberboats/mattresses) that also can suck (if it's tube is put in the other hole) and then suck fuelline 3+4 with it. Or blow air through the #4 float valve opening upwards after you've removed float and float needle. Can be done with compressed air or even a bicycle pump.

[alacrity]

can also be done with a vacuum... try a hand vacuum/Dustbuster with something you can sleeve down the orifice to connect to a tube.
I have a "fitting" for my shopvac... one of the plastic extension tubes that has 3 decreasing diameter rubber tubes duct taped into the end of it - the final one is 3/8" id.  It makes a pretty strong highly localized pull.