Topic: CB 550 K 76 Fuel in airbox

[Lars]

Got a call the other day by a guy who recently got a CB 550 K 76, low miles. He said that fuel was flowing out from a tube below the bike and it was not from any of the 4 overflow tubes from the float bowls. It was from another thicker hose from the air box. I have never experienced anything like that, but then I remember I (think) I saw a thread about this on this forum, but careless me did not read it. Can anyone give me an update on this issue? Petcock not closed, pressure down on non operating float bowl needles, pressing fuel up into carb venturi and flowing back into the air Box?
Lars

[revchuck]

im having that issue with a 650 as well.   i believe the float in #2 was/is sticking  and dumping into the air box .  i have a mower that does the same thing  except it fill the crankcase.  typically i shut my mower off tank off and let the mower run out of gas to avoid the problem.     

[flybox1]

sure it was fuel and not condensed vapor from the breather cover?
unless standpipes are blocked AND your float valves/floats are inoperable, fuel cannot flow upward and into the airbox, it would drain out the overflow tubes first.  check for bad float valves, floats stuck down, and blocked bowl overflow tubes.
remove the tank and carbs and check all the hoses, and maybe install new orings on the connectors between bowls.

[mronegear]

could it be from the venting tube under the gastank?

http://www.cmsnl.com/honda-cb550f1-super-sport-550-four-1976-germany_model17116/partslist/F12.html#results

It is shown in the graphic... and a k model should have it, too ;-)

cheers!

[Lars]

Flybox1, I agree with your logic thinking. I asked him if it really was fuel on the ground which he confirmed. So. Both stuck standpipes and no operating float valves??
Not very likely, I have never been close to experience that. I will ask him a few qustions to check out this issue.

[mono]

if he was running way too rich would that cause the breather cover to put out enough vapor to condense in the airbox drain make it look like there is a leak?

that's a real head-scratcher.

but i have never had fuel *pour* out of anything except a float tube.

[flybox1]

 too many things have to be working against him if the fuel is really coming up from the bowls and into the airbox.. but it could happen i guess   
i would head right to searching for some blockage at the fuel lines and n the carb bodies themselves.

[mono]

maybe he has the fuel line from the petcock reserve run to the airbox.

[flybox1]

^   ...trying to one-up Hondaman!?   

(..in reference to Hondamans 750 book, and the carb bowl tubes mod)

[revchuck]

im positive mine was fuel and the air box was full all the way to the breather.   

[Lars]

Mono, that would explain it, LOL
I will Call the guy today and get some more info.

[mono]