Cause of Carb leak??

[zookey]

Hi guys......... someday we may actually get to ride this bike.

So he has been cleaning carburators for days, he replaced the float needles and seats.......... but we still have a slight leak or whatever from the 3rd carb (see picture)



any ideas of what would cause a leak at this hole?
Sorry I don't know all the technical names for stuff but he wrenches and I computers.

[red bandit]

The float needle has a slight leak.

[zookey]

The needle and seat are brand new just out of the packet..........
So you are saying the needle isn't seating quite right, so how do you fix that??? If we adjust the float would that make the needle seat better?

I am sorry to sound so "duh" but I have to understand what I am trying to tell my husband he needs to do to get this bike on its wheels!

[boyat68]

zookey:

That passage is an air port to the fuel bowl. When the bowl gets too full, fuel leaks out of that passage as well as the one on your left and also out of the throat of the carburetor. It also leaks out of the front of the carburetor and into the piston area, down the sides and into the oil sump. This may dilute your oil and cause a problem with the lubrication of your main bearings. That is why many on this board recommend that you change your oil if you have had a consistent fuel leak.

Leaks are caused by the valve seat assembly not sealing correctly because of a fiber washer malfunction on your 79 carburetors. It could also be caused by the needle valve not seating correctly to stop the flow of fuel. This flow is maintained by your floats pressing down on the needle valve as the fuel bowl fills up. It could also be caused by your floats rubbing against the sides or forward edge of the fuel bowl seizing them and not letting them press against the needle valve. It also could be caused by a piece of debris (trash) between the needle valve and the seat. Note that the 79 and 80 carburetors needle seat arrangement are different. The 79 had a screw in seat with a fiber washer so you may want to check to see that that washer is present, as that is one area that leaks (seeps) fuel bypassing the needle arrangement. The 80 had push in seats with an "O" ring sealing and a clip holder.

I had a dickens of a time stopping my 80G carburetors from leaking, even after replacing all new parts. I finally found that my floats were rubbing on the sides of the bowl see: http://www.xs11.com/forum/showthread...hlight=boyat68

[boyat68]

zookey:

You may want to peruse the excellent write up of Ken Talbot's sight gauge method of setting floats found at: http://www.xs11.com/tips/maintenance/maint20.shtml

I endorse this as the many times I had to remove and check the carburetors due to leaking fuel.

[Wildkat]

hey zookey,

May or may not be it... but something else you might check...

I just replaced a float needle and after getting everything in place... still had a leak... Seems the rubber tip was offset (it came like this from the package) just enough to let the needle get hung up and it wasn't seating properly...
Also, sometimes the little tab on the float close to the posts will get hung up and not allow the float to move...

Hope this helps...

[boyat68]

zookey:
Another thread that you may be interested in.

http://www.xs11.com/forum/showthread.php?s=&threadid=1376&perpage=15&highlight=Fuel%20Bowls&pagenumber=2

[garyramir]

bottom line its the engineering what is at flaw. metal tip float needle is my nightmare 79xs1100. its an ongoing battle that most of us should not have to endure if it were just made correctly with rubber tip. should of had recall back then to prevent all of this craziness. i think the gas fumes are too much for me...need ventilation...

[bikerphil]

You can adapt viton tip needles to fit the early type XS carbs by using 82 Virago 920 needle and seats.

You do realize that this thread is over 15 years old

[Radioguylogs]

Some of my bikes have metal tips, as they were designed, and they work fine.

Perhaps you have some crud in there?

[cajun31]

bottom line its the engineering what is at flaw. metal tip float needle is my nightmare 79xs1100. its an ongoing battle that most of us should not have to endure if it were just made correctly with rubber tip. should of had recall back then to prevent all of this craziness. i think the gas fumes are too much for me...need ventilation...

You resurrected a 15 year old post to state that the metal tipped needles are a design flaw? Yamaha recognized that to not be the best design and in their later carbs they changed it. The later carbs have Viton tips on them. By the way your bike will run just fine on those later carbs. You might want to consider acquiring a set of them. One other thing that you might want to consider is don't run ethanol gas. Ethanol free is much better for these old bike. Rather then commenting on a 15 year old post, just start your own post and go from there.