TOPIC:

These come in a matched pair for good reasons.

float needle and seat

And what about the inline fuel filter as already suggested?

Many a perfectly sealing float needle/seat interface is instantly fouled by the first onslaught of incoming fuel containing grit or crud being allowed into the carb from failure to use an inline fuel filter.

Am thinking you likely already know as much or more about this than many shops.

Good Luck!

Have put in an inline fuel filter ... it is a paper type for cars from pep boys. Does the same thing right? hehe. Had a thought after reading a similar post on another forum. What about vapor lock inside the float bowl? Here is the nifty pic i saw on another post:



Sound feasible? I will re-check all my connections tonight and "fine-tooth-comb" the carbs once again.

I was not aware of the valve and seat coming as a matched pair, is it crucial to have these paired, or are they interchangeable within the same set of carbs? If not, that may be my problem.

Never had a puddle under the bike, but from time to time, it would have about a tablespoon worth of spillage out of the drain lines from the carbs. when leaning it off the kickstand to fire it up and go.

Zephyus wrote:

... was not aware of the valve and seat coming as a matched pair, is it crucial to have these paired, or are they interchangeable within the same set of carbs? If not, that may be my problem....

Each float needle/seat combo should be kept together as a matched pair. It would be okay to put the matched pair combo in a different carb. But should not interchange the float needles with different seats.

Stated another way, the float needle that seals perfectly with one seat may leak when paired with a different seat.

But none of this addresses the reason why the float bowl overflow circuits are malfunctioning and allowing fuel to rise up into the carb throat.

In any event, the floatbowl vent hoses to outside air should be clear and unclogged. According to the diagram, a clogged vent hose could cause fuel to rise up into the carb bore, but my experience is limited to situations where overflow malfunction alone allowed the fuel to rise with perfectly clear floatbowl venting.

Good Luck!

Pulled the carbs and removed float bowls only. Hooked fuel line up to can of air. With the carbs sitting upside down and using gravity to close the needle/seats, i moved each float while forcing air into fuel line. Each float stopped the compressed air, and let it by when the float was pulled up from the needle/seat. So, float valves are functioning properly. Tested to see if floats are floating, and they do. Hmmmm. Net will be high pressure compressed air through entire carb body and every orifice i can see, once again.

If that doesn't resolve the issue, does anyone have a set for sale - already tuned for pods and open exhaust? HAHA

In any case, I am thinking about sending them in to Wired George to have them rebuilt. Anyone have any dealings with him?

OK ... got a few pics, and have isolated where the fuel is coming out from.


If you look at the opening into the carb body, you see one cast in opening to the left, and one closed off opening on the right. In the middle near the bottom is what looks like a brass fitting inside another opening. The fuel is spilling from these holes and not coming through the main jet.

Any thoughts?

Image for previous post. Leaking area circled in red

Issue fixed .... well sorta.

Crankcase breather has a K&N pod filter on it with a tee bracket on top for the lines from the carb tees between 1 and 2, and 3 and 4. This tee was forcing air back into the 1 and 2 carbs which in turn forced fuel out of the float bowl and into the air filter. Disconnected the lines from the crankcase breather and viola, no more leaking fuel.

Now I just have to sync the carbs and do some minor adjustments. Thanks for the replies, I love picking the brains of those who may know more than me.

I ain't a carb guy but if your carbs are anything like my BS34's that's an airjet. If fuel is coming out of there, I'd say it's float level which means it's not seating. Even if your overflow is clogged the gas level, in the bowls, shouldn't get to the point of overflowing from either the overflow or that hole (jet)... which still means the needle valve is not seating. Get new sets of needles and seats. Do you have rubber tipped needles or metal?

If I understand correctly, the crankcase breather is/was connected to the carb venting lines?

This would cause any over flowing fuel to go into the crankcase and mix with the oil. The crank vent might actually suck gas into the crankcase Not a satisfactory situation at all.

If this is the same design as my 650-B1, there should be no such connection. The over flow lines should hang down below the engine and be connected to nothing. The lines should be free, unobstructed inside and breath freely. Test each overflow line by blowing into it. Replace if required.

If that's the real cause of the symptoms then it’s a real easy fix... and dirt cheap. Congrats!

Best of success.

Not sure if these are the carb venting lines, but this is how it was setup with both lines from the carbs to a Tee which sits on the top of a pod air filter on the crankcase breather. I have highlighted the Tee between the carbs and the hose to the crankcase breather. I have never smelled gas in the oil, and it has been run like this all summer. Just recently started giving me fits after a carb rebuild.

Those are the vents. They should have a piece of hose on each and the hose should be routed over the swingarm. The hose must not be crimped or plugged in any way. See our VM Carb Connections tech page on our website as the Mik VM series carbs have similar connections. It is under wg's Tech Stuff Index.

Zephyus, also noticed that the float bowl overflow nipples at the bottom of the carbs are not used. There should be one hose on each of the four nipples and they should go over the swing just like the two two carb air vent hoses. Don't want gas on a hot engine.

Including the battery overflow hose there should be a total of 7 hoses coming out the bottom of the bike:
- 2 carb air vents,
- 4 carb fuel overflows and,
- 1 Battery overflow.

Best of success.