fuel in air box

[bbs1980xs1100g]

at idle i get a little backfire ,sluggish starting off, I pulled the tank and the petcocks are not leaking i have them down(on) no leak.

I pulled the carbs i took out one float, needle, and seat. everything is very clean I cleaned the carbs a year ago 4k miles ago, what do I look for? the floats looked in line (level) the bike runs fine past 20 mph, the seat was a little hard to pull out, the o ring was slightly worn? tia for help, oh yea its an 80g

[yamahansolo]

the little rubber parts might be no good. i have had this happen with 3 different bikes. i would drain the oil, clean out the airbox and only put about a gallon or so and see where it's leaking from.

i let a bike sit for a couple of days after putting in an off brand fuel treatment and i went out and saw the fuel had drained into the motor and out the shifter and ate up the blacktop under the shifter!!! ooppsss...

[blue giant]

Pretty common problem with these bikes. You may have to replace the
o-rings around the seat body. Make sure the floats are not sticking to the sides of the bowls or that the floats drop to low and allow the needle to bind in the seat.

Do the seats slide in and then are held by a Y bracket and screw or do they screw into the carb body?

Paul

[bbs1980xs1100g]

yes y bracket, they just pull out with needle nose, the oring looks a little worn could it be the oring around the seat, It looks like the needle is closing

[bbs1980xs1100g]

the seats are tight, I dont know if that would be it, and also when i put it back together should i put the airbox back on just for a test ride?

[tarzan]

It definitely could be the oring under the seat.
I would ride it around a little bit before you put the airbox back on as long as there isnt a bunch of dust in the air,just to make sure the carbs dont leak.I would suspect that you would pretty much know if they still leak right away though.
Also check real close at the tips of the needles.If they have an iregularity where they seat in the seats they will leak too.

[bbs1980xs1100g]

the rubber covers over the 12:00 jet from the main jet or 6:00 (depending which way you look at itjet covers are very loose? any suggestions? and also I lost a washer under one of the main jet screws, i guess its just a brass washer can i use any washer in place

[TopCatGr58]

Hey BBS,

I haven't looked for your other posts, so I can't tell the specs on your carbs, but what you said about the rubber plugs caught my eye!

The jet tower other than the MAIN JET is the PILOT JET tower. Yamaha was in the transition from the 78/79 carbs that used larger mains ie. 137.5 due to a SHARED fuel supply, via a little tunnel between the main jet and the pilot jet tower vs. the 80/81 style. The pilot jets were capped/plugged to control fuel, to keep it flowing from the bowl, thru the main jet, thru the tunnel, into the pilot jet and then thru the carbs to the engine. The 80/81's feed the main and pilot jets directly from the bowl, hence the smaller mains.

Another piece of this puzzle is that the MAIN JET Nozzle/emulsion tube has a hole in the side near the end where the main jet screws into, this is to allow the fuel to travel thru that tunnel into the pilot jet tower.

So....IF you have both that tunnel, and the side hole in the emulsion/nozzle, then it should have the pilot jet caps/rubber plugs, so that fuel WILL use the main jet/tunnel/nozzle route thru to the pilot jet. But if your carbs don't have that tunnel, side hole in the nozzle, then the pilot jet will be getting its fuel directly from the float bowl, and the rubber pilot jet caps are NOT to be used.

THose caps come in some kits that can be used with both earlier and later models. IF you put them in at your previous cleaning, and you don't have the pilot to main jet tunnel, then you're starving your pilot jet/idle circuit.

Surprisingly, a few folks with these bastardized carbs needed the pilot jet caps, however they still had the later designed smaller MAIN JETS...ie. 110~120 sizes, vs. the older 137.5 sizes!?

SO....need to inspect your carbs for the above descriptions/characteristics, and then plug or UNPLUG them accordingly!
T.C.

[bbs1980xs1100g]

Hey BBS,

I haven't looked for your other posts, so I can't tell the specs on your carbs, but what you said about the rubber plugs caught my eye!

The jet tower other than the MAIN JET is the PILOT JET tower. Yamaha was in the transition from the 78/79 carbs that used larger mains ie. 137.5 due to a SHARED fuel supply, via a little tunnel between the main jet and the pilot jet tower vs. the 80/81 style. The pilot jets were capped/plugged to control fuel, to keep it flowing from the bowl, thru the main jet, thru the tunnel, into the pilot jet and then thru the carbs to the engine. The 80/81's feed the main and pilot jets directly from the bowl, hence the smaller mains.

Another piece of this puzzle is that the MAIN JET Nozzle/emulsion tube has a hole in the side near the end where the main jet screws into, this is to allow the fuel to travel thru that tunnel into the pilot jet tower.

So....IF you have both that tunnel, and the side hole in the emulsion/nozzle, then it should have the pilot jet caps/rubber plugs, so that fuel WILL use the main jet/tunnel/nozzle route thru to the pilot jet. But if your carbs don't have that tunnel, side hole in the nozzle, then the pilot jet will be getting its fuel directly from the float bowl, and the rubber pilot jet caps are NOT to be used.

THose caps come in some kits that can be used with both earlier and later models. IF you put them in at your previous cleaning, and you don't have the pilot to main jet tunnel, then you're starving your pilot jet/idle circuit.

Surprisingly, a few folks with these bastardized carbs needed the pilot jet caps, however they still had the later designed smaller MAIN JETS...ie. 110~120 sizes, vs. the older 137.5 sizes!?

SO....need to inspect your carbs for the above descriptions/characteristics, and then plug or UNPLUG them accordingly!
T.C.

its an 80g it has carb passage plugs that are loose,i scuffed up the top of the float valve bodies(seats)? pulling them out to clean. Could the top cause a leak or should i just try replacing the oring around the body? tia for your time i havent been on this forum in years, damn good bikes

[blue giant]

yes y bracket, they just pull out with needle nose, the oring looks a little worn could it be the oring around the seat, It looks like the needle is closing

That was the problem I had. I cleaned the carbs til the cows came home and it still leaked fuel out throught the air box and flooded the oil as well. Replace all 4 and no more leaks.

[boyat68]

bbs1980xs1100g:

As TC said, "a few folks with these bastardized carbs needed the pilot jet caps," and I have a 80G that does and those rubber caps for the pilot tower are loose, but are held in place by a raised pedestal in the float bowl. The most prevalent thing that I found with my carbs was the plastic floats were binding against the sides and the drop of the floats were too much. I used Ken Talbots fuel check setup to check the float level and leaking of the carbs before I replaced them on the machine. I would let them set over night and then mount them back on the machine, but they would leak. I had found that letting the bike lean on the kick stand would cock the floats to one side and hang while filling up. Off the bike they would come and I would go through the setup again paying close attention to lean the carbs on the setup apparatus while checking the filling and level of the floats. The floats would still hang after 10 0r 12 fillings from the tank. The floats were not adjusted correctly, so apart they came to reset the tangs or bend the floats away from the sides. See the thread http://www.xs11.com/forum/showthread.php?t=20035 as I believe that he has the same problem with the plastic floats. "egsols" Earnie has a solution for the mounting stand. He suggested that we use a piece of angle iron to hook the bank of carbs on while testing the leaking using Ken Talbots setup rig. The process is time consuming at first, but each time you gain experience and familiarity with your carbs. Do a search on cleaning carbs and you will find many good suggestions of what to look for.

[skids]

There is also the possibility that the pivot-action of the float on the pin is buggered. I saw one that had "rust" (or something) that prevented smooth movement.

[bbs1980xs1100g]

I put new orings on the seats(valve guides) push in type, and reassembeled except air box, seems to be working, the gas leak would leak very little after 30 miles, then drip through the airbox, would stuck floats cause a big leak or does that vary?

[boyat68]

bbs1980xs1100g :

What I believe happens is the bike will use fuel presented to it by the floats during a hard run even if the floats are not adjusted properly. That is the amount of fuel flow equals the use even if the floats are sticking or do not shut off. When you park the bike, the fuel continues to flow, and it takes a few minutes to fill up the spaces in the air box before it leaks down the sides of the bike. A wet left leg and fuel on the floor usually indicates this. Some have put a shut off valve between the tank and the carbs to prevent this and shut the fuel off immediately, and the little bit in the air box evaporates. Getting those floats adjusted is a PIA, but once you get it no more fuel in the air box and a dry leg all through the ride. The other consideration that you have to look at is the possibility of fuel going through the engine side and leaking into the cylinder and down into the oil. The carbs are mounted with a slight rearward slant and the barrel of the rear part is lower than the front part, but fuel can leak down the front if the flow is too great.