Topic: Leak at float bowls - '78 CB550

[man-bot]

Hi there,

Just bought a '78 CB550 and it had been leaking formt he carbs so I took them off cleaned and bench synched them... put it all together and to my dismay carb #2 leaks badly - but from the float bowl at the gasket.  I put all new gaskets on when I cleaned the carbs...  nto sure where to go next. 

The float seems the same as the other 3 carbs.  Could it be a sticking float needle?  Is the gasket not seated properly on the float bowl if it is leaking out of there?

All thoughts are welcome!

[mossen]

I'm having the exact same problem with the exact same bike...With the bowls off I can push the needle into the seat and gas does not leak out. Install the floats and hold them parallel to the float bowl mating surface on the carb body, and gas does not leak out. However when I put the bowls on and let the gas down, it leaks out from the gasket area. Pretty badly too. And yes the float floats and it pivots easily on the hinge. First thing I would do is the clear tube test to see how far the fuel is coming up...that should at least tell me if the floats are set correctly and the needle seat is working.

Let me know if you solve this problem...

[flybox1]

Is the gasket not seated properly on the float bowl if it is leaking out of there?

YES
if your floats are set and lifting properly, they will shut off the flow of gas before it reaches the gasket seam.  one might have stuck down when the bowls were filling, allowing the bowl to overflow.
drain the carbs and reinstall the gaskets. you probably pinched one of the gaskets in the process of reinstalling.

tip...
after you reinstall your carbs, and turn on gas for the first time to fill them, fill them slowly, and gently bang on them with a ruber mallet to jostle the floats free as the gas lifts them.  they should then shut off the fuel from overflowing the bowls.

[man-bot]

Well I'll pull the bowl off tonight and check & reseat the gasket.  When you say to fill them slowly I assume you mean don't turn the valve from off to directly on... kind of 1/2 way and knock the bowl (while looking for overflow).

Haven't had the bad boy running and I'm this close to it... would love to have it ride-able for the long weekend (in Ontario) coming up!!

Thanks!  I'll let you know how I make out.

[man-bot]

Well I found out I had the petcock output tube going to the wrong port on the carbs! I have switched the lines so that the petcock goes to the connection on top which has the bulbous end (the fuel port)... but no gas gets to any of the carbs but #2 now.  When it was attached to the port without the bulbous end (the vent?) gas flowed to at least carbs 1 and 2, but also flowed all over the place because the tube was too big... (oh and on the vent not the correct port).  Stupid I know.

So the big question is - why won't gas flow into my other carbs??  I have checked and it flows just fine from the tank.

Hoping someone can help.