Fuel pouring from carbs

OK. First, the XJ700N carbs have tons of hoses everywhere. From chacal's parts list:

So, after thoroughly cleaning my carbs, squirting chemicals into my eye from the tiny pilot hole, replacing my throttle shaft seals, etc., i got my bike running.

While running, it started spewing out fuel from the overflow tube between #3 and #4, as described above by chacal.

Now, I gather from earlier posts I found doing a search that the culprit is probably a stuck float valve.

http://xjbikes.com/Forums/viewtopic/t=19948/
http://xjbikes.com/Forums/viewtopic/t=8575/

Assuming that's the case, I'm having trouble with the "how" of it. How does a stuck float valve cause fuel to overflow? Or, to put it differently, if the valve was working correctly, and closing once the bowl is full enough, what would happen to the fuel flow from the tank? Would it stop? What if my petcock was set to Prime?

I'm having trouble wrapping my head around this mechanism.

So, two questions: 1) is my diagnosis correct? and 2) how does this work?

thanks.

 

a stuck float will allow fuel to keep coming in to the bowls and flooding. When you had your carbs off, im guessing you didn't take your floats out?

I just dealt with a stuck float the other day. When your carbs are out and bowls off, take the float pin out. remove the pieces and keep them seperated for each carb.

What i used was a little piece of sandpaper roll it up and sand inside the shaft where the pin goes through. This did the trick for me. Make sure not to bend the tangs on the float themselves. as this could cause the floats to not allow for a propper seat.

 

steber - thanks, I did do that when I had my carbs apart.

I guess what I don't understand is how a functional float bowl STOPS the flow of fuel. If the fuel can't enter the bowls, it's still flowing from the tank, isn't it? Where does it go?

I think I need a fuel flow diagram.

 

This may be oversimplifying it, but go take the lid off your toilet and see how it works, that's if you have the type where the float raises in the tank.
Does this make sense to anyone else?

 

Perfect sense! Are we still allowed to say "Ballcock" or is it a new, politically correct "Float valve"?

I wonder if it becomes confusing when we work on the jets etc upside down?

 

When the needle valve stops the flow of fuel, it STOPS. For instance; when everything is working correctly, and the bike is OFF but the fuel tap is on PRI (allowing fuel to flow regardless of vacuum signal) and the floats are working correctly, they all shut cleanly off and NO fuel flows. The needles will hold it back. However, if one or more floats DO NOT shut off cleanly, then the carb(s) will overflow.

If the tap is in the ON position, but there is no vacuum then the fuel tap should not allow flow.

This is why the "fuel in the oil" syndrome is caused by BOTH a petcock that isn't shutting off, as well as a float that isn't also.

 

a possible cause too would be the float tang got bent. float level is too high.

 

losifer, if you don't think your floats are getting stuck somewhere, check this out. with the carb upside down, remove the float needle valve and check the tip, it should be Perfect. Next, get a flashlight and a magnifying glass and look into the needle hole, see the little hole at the other end (that the needle mates with)? check the edges of that hole for small burrs or imperfections. Mine had one and took me forever to find, Forever. I actually shipped it to Chacal for confirmation that it was junk. How bout the Clear Tube Method for checking the fuel levels, did you do that? If not do a search for it and let us know