Prefice. . .this is only the fourth bike I have rebuilt carbs on, so I'm just learning.
1977 CB550F
I just rebuilt carbs: replaced gaskets, o-rings, cleaned jets and needles, set float height. I also set valve lash and routed new fuel lines with filter. Bench-sync'd rack and new throttle cables, too. . .
When I turned the fuel on, man were those bowls hungry! I soon realized that Carb #1 and #2 were flowing fuel from the brass overflow tube coming out of the bottom of the bowls. #3 and #4 were not, but I then realized this was due to the fact of the fuel line routing: as you know, the T connector that splits the fuel line into two fuel lines leading to 1&2 and 3&4, is on the 1&2 side of center and (in my case) a little lower than the highest apex of line for 3&4. So, if the float valve is not stopping fuel on the 1&2, there will be no pressure to feed 3&4. So, I crimped off line to 1&2 to feed 3&4 with fuel. This worked, but then 3&4 also started flowing a steady stream of fuel from their overflow tubes.
Before I rebuilt the carbs, fuel was reaching the bowls and not overflowing: float valves worked. During rebuild, I replaced o-ring on float valve seat and cleaned float needle. I used worn out 800 grit paper to smooth pathetic-looking hinge pins and washed them. I set float height w/ metric ruler, checking both floatants to ensure level. I measured when the tab was just touching the needle, but not depressing spring. I measured from surface of carb body in which float bowl seats to apex of float. I set all at 22mm.
I believe carbs are 069A. . .is that correct for this model or am I forgetting? Float valve needles are all metal, no rubber tips.
So, before I pull these off and open them up again and scratch my noggin'.....
Anyone think they KNOW what went wrong? Because I don't!
I routed the single fuel line under intake #1, so it goes below the bowl on its travels to the T joint.
Thanks!
