In a previous post I mentioned I picked up a 1985 Honda Sabre, fresh out of sitting in a garage for years.

I've started getting in back into running shape but ran into a carb issue that I can't quite pin down.

I took the carbs off the bike to clean them and after that was all said and done I put them back together (mostly) and checked float valve operation by putting gas in the fuel line and manually opening/closing the float with my hand (i got burned bad by this on another bike, leaked gas into the oil... not pretty). so after that checks out, i put the carbs back in the bike (which is a pain with four carbs, by the way). I start the bike, which starts up easily enough, but i notice the fuel level dropping waaaaay too fast. I have a clear fuel hose running into the carbs for now (the tank is off the bike) and it drops about an inch every few seconds, maybe going through 1/4 cup of gas a minute. it might also be important that the bike won't idle without choke out, and dies if you rev it.

pull the plugs, and one is soaked! pop the carbs off, check the floats and gaskets again... everything checks out.

what could make a carb that seems sealed and in sound condition drip fuel like it is it's job when the engine is running?

i think my next diagnostic steps are going to be swap the float valve and float from the presumably leaky carb into another one and see if the problem travels with those parts. otherwise, i'm not sure what else i can do.

thoughts? bad float valve? dirt/particles messing up the seat? some overflow channel being activated?

You might ask yourself why I've come here rather than go to the bike's forum, and i would say, first off, everyone here is sooo much cooler   and more knowledgeable   and what's that you say? something brown on my nose? oh, well i guess it is also because this bike doesn't have a forum, which leaves me feeling sad and alone  :'(

It's almost impossible to tell if a needle is properly seating by holdng the float with your hand. Too easy to apply more pressure than the float would.
If you want to check them before reinstalling, put the float bowl on & attach the carb to a fuel supply. Hold the carb in the same position that it would be on the bike & turn the fuel on. If it leaks you have a bad needle & seat.
There is always the chance that something in the tank (rust?) will break loose & cause a needle & seat to leak, or clog a jet or a passage. Sometimes it just takes more than one cleaning to get everything.

spacepirates wrote on 01/10/12 at 07:44:01:

The floats need atmospheric air pressure in order to float properly.  A clogged vent will cause abnormal high air pressure above them, mucking up their ability to float at the right level.  I saw this problem on a gs500..only two carbs, but the principle should still hold.

Also, we assume you have checked the floats for any pinholes and are sure they are not getting waterlogged.

Ever noticed how your bike runs different with a full tank of gas than just before you go to reserve? That is the difference in fuel pressure. With a gravity feed fuel system a carb that may not leak with just a little pressure may flood with the correct pressure supplied.
I prefer to put a longer fuel line on my tank so I can rest the carb on the floor while checking. This applies more fuel pressure to the carb. If you're worried about making a mess, set the carb(s) in a drain pan.

It sounds like you have a pretty good grasp of what to do. Just clean anything that looks like it could be a passageway & you can't go wrong.

One of the SOHC4 forum guys might be familiar with your bike.
They tend to be brand loyal.

Take a clear line and run it from the drain up.
turn on the fuel and see where the fuel comes up to.
shouldn't rise above the bowl gasket.

are the float valves rubberised?

verslagen1 wrote on 01/10/12 at 09:00:03:


I'll scope out the SOHC4 forums. Didn't even know they existed...

The float bowl in question doesn't actually sit flat in this v4 design. the float bowl is at a 45 degree angle or so from level, meaning the gasket is offset from level. I'll try the clear tubing, but the lower lip of the bowl is very close to the lowest point of the bowl itself (i think). I can't imagine the fuel level *not* being above the bowl, but i'll check.

Serow, I'll double check the jets. if i recall correctly, the main jet screws into the brass tube which screws into the carb. i guess it could have come loose or not been tightened enough.... but then i'd only have myself to blame  

re-cleaned the carbs, blasted any thing i saw with cleaner and picked up a carb cleaning tool to wire out the jets.

put everything back on yesterday, but spent most of my time getting a new carb put on my savage. if this week is warm enough this week or this weekend I'll try out the Sabre again.

Of course, I still need a title for it, but that won't stop me from a little joy ride