Topic: CB550 Leaking Carb... Out of the front?

[Joe Danger]

I checked the carb faq, to no avail.  After several dis- and reassemblies, I've got a leaking #1 carb.  The thing is, it's leaking out of the right of two brass tubes at the bottom of the intake side.  The leak starts as soon as I turn the fuel on, and is stopped by manually raising the float.

What is that tube, and what's in there that's causing this?

Thanks.

[paddy paul]

check to make sure your float is moving freely, and make sure its at the proper height

[Joe Danger]

Well, I checked the float height, and reset it to exactly 14.5mm, and it's still leaking.  Does anyone know what that right bronze tube in the air side of the PD carb is/goes to?

[TwoTired]

Are you asking about tubes inside the carb inlet mouth or outside on the body of the carb?

[Joe Danger]

I oughta check my posts more often, sorry about that.

Yes, the tubes in the inlet, on the interior.

[chickenman_26]

That tube is the air bleed for the main jet's emulsion tube. If fuel is leaking from there, it should come out the bowl overflow first. Maybe your overflow tube is plugged. But fuel wouldn't leak from either place if the fuel level was correct. Question - how are you lifting the float manually with the float bowl attached?   

Stu

[TIM TINGEY, age 55]

THE FLOAT VALVES ARE NOT WORKING EITHER DUE TO A FAILED AND WORN VAVE, OR THE SEAT IS NO LONGER FLAT AND ROUND. ALSO THE FLOATS ARE TREATED CORK, THIER PLENTY OLD ENOUGH TO HAVE BECOME SATURATED WITH GAS. PUT THEM IN A GLASS OF WATER-THEY SHOULD ALL FLOAT AT THE SAME HEIGHT AND ATITUDE. MAKE SURE THE FLOAT VALVE/SEATS ARE'NT DIRTY AND SET THE FLOAT LEVEL AT 12.5 MM.

[Noel]

WHAT? SPEAK UP!

[chickenman_26]

...THIER PLENTY OLD ENOUGH TO HAVE BECOME SATURATED WITH GAS. PUT THEM IN A GLASS OF WATER-THEY SHOULD ALL FLOAT AT THE SAME HEIGHT AND ATITUDE. MAKE SURE THE FLOAT VALVE/SEATS ARE'NT DIRTY AND SET THE FLOAT LEVEL AT 12.5 MM.

Closed cell foam, not cork. But funny you should mention that. I had a friend last week testing his floats in water, and they floated fine. I told him to try a bowl of gasoline, and they sank. Water is heavier than gasoline, so things are more buoyant in water. Also, his '77 model uses a 14.5 mm float level. 12.5 is for the '78's PD46 carbs.

Stu

[Joe Danger]

Question - how are you lifting the float manually with the float bowl attached?   

To be completely honest, I don't remember.  I'm a grad student, and October 3rd is a midterm week, as was last week.  It's probably best to ignore most things I say during midterm weeks.  I'm gonna go check the float height again, with hose, and check my assumptions.  On these floats, it's flat side down, shaped side up, right?

[Rosinante]

Many years ago, my 750 carburetors leaked because they overflowed.  They overflowed because there were HARD plastic bits in the fuel rail, and those bits were lying on the tips of the valves that poke into the rail.  How they got there is still a mystery, after more than thirty years.  I suspect they were petrified bits of fuel hose.