Motorcycle Repair: fuel leaking out of carb float bowl, v45 sabre, fuel pump filter

Question
QUESTION: I have a 1983 Honda 750 Sabre/V45. It was fine a few days ago and I reconnected a choke cable. Now when I start it it is leaking ALOT out of the right front carb. The guy i bought it from rebuilt the carbs and said it may need a new bowl gasket. I have ordered one, but it seams to be pouing out of the nipple at the bottom of the float bowl. I turned the screw that you use to drain the bowls and it lightened up a bit. Then i tapped the bowl lightly with a socket wrench and the flow sped up again. What would cause fuel to pour ot of a carb when two days ago i put 60 miles on the bike and had no leaks. I did put some seafoam in the tank, could it have eaten the gasket. Is there an o-ring on the bowl emptying screw that could have went bad.

ANSWER: Brian, fuel flowing from the overflow nipple is indicative of a leaking float valve. Either the needle has gotten cocked in the valve seat and is not closing or some crap got in between the tip and the seat. The Seafoam may have loosened something up, but the filter should screen out anything coming from the tank or petcock.

You might try starting the engine, with the fuel on until it starts to leak, then shut off the petcock and let the motor burn off the fuel in the carbs. While it is running down try shaking the whole bike back and forth with the handlebars, then turn the gas back on again... repeat a couple of times, in case the float needle is just hung up a bit. If it won't stop flooding over, then you are going to have to pull the float bowl/carburetors to find out what is happening in there.

The drain screw does have either a gasket or an O-ring on the end.

http://www.bikebandit.com/houseofmotorcycles/honda-motorcycle-vf750s-v45-sabre-1

Hopefully, you didn't bend/break any of the interconnecting fuel tubes or disturb their O-rings to cause additional leaks, when you were hooking the choke cable back up. Check your inlet lines coming to the carbs from the fuel pump/filter and make sure that they are all good and tight, with no signs of cracks.

Bill Silver


---------- FOLLOW-UP ----------

QUESTION: Bill,
I appreciate your quick response. I tried to shake the bike but it didn't work. I have never broken into a carb before; when I take off the float bowl will I see a little spring loaded thing hanging there that I can tap with my finger to free it from sticking. Is there some type of screw you turn to adjust it so it shuts off. If you have any suggestions where I can find a schematic or picutres I would appreciate it. Also, do you know where the fuel pump is.
Brian

Answer
Brian, go back to the bikebandit.com site reference and you will see the fuel pump. It should be under the seat, perhaps along the side cover. Been awhile since I worked on one.

The float valve is just a plastic float that rises when the incoming gas fills the float bowl. The shut off function is a small needle that is pushed up into the float valve seat and shuts off the fuel flow when the bowl is full to the specification that Honda designed. In some cases, the float valve seat is sealed into the carb body with an O-ring and after 25 years, the O-rings fail, causing a leak. It is not adjustable, unless the float has a metal float tang that contacts the needle.

http://www.dansmc.com/float.jpg

Bill Silver