need help- lost

[oldyam80sg]

Today i took off carbs because i wanted to see why my #3 carb kept on weeping a little gas.Took off float bowl and removed float.The needle valve looks a little worn on the one side and will soon be replaced.Put carb back together and went to start bike.All cylinders are hot except i assume # 3 cylinder.It is slightly warm at best.All other cylinders are hot as i spritzed some water and they steamed.#3 spark plug does not seem to indicate that it is even firing.I'm getting spark and #3 float bowl has gas in it .Where do i go from here?All other plugs are wet with gas except #3.

[GNEPIG]

The next check: would be to check to see if there is sufficent amount of fuel in the #3 float bowl. Open that little drain screw on bottom of bowl to see, or remove carbs then float bowl. Compare with amount in the other bowls.

[boyat68]

oldyam80sg:

Assuming that your #3 carb was feeding fuel although it was weeping before you worked on it. You could have misaligned the float height where it does not allow fuel in the bowl or as GNEPIG said, "...check to see if there is sufficent amount of fuel in the #3 float bowl." Your pilot jets may not be able to pick up enough fuel to take it up to the 4000 mark where your mains cut in, or your idle Pilot screw may need turning in a 1/4 turn or more to make #3 idle properly. If once you have it started, see if it will get hot when you raise the RPMs above 4000. This will indicate that your pilot jets are not feeding fuel Remember that the pilot jet sits above the plane of the main jet and on the 80G and SG, and have a rubber plug that blocks off the pilot tower and forces the main jet to supply fuel through a hole between the two towers. Unless you have earlier Carbs such as 79 carbs in the 80SG. Another thing that I noticed on my carbs was the tendency of the needle valve spring keepers to disengage from the needle valves and wedge between the needle valve and the float height tang. Also the rubber plug could be knocked off while re-assembling the carbs.

[oldyam80sg]

Where is the rubber plug located.? I undid screw at bottom of bowl and fuel poured out-maybe 1/4 cup.

[boyat68]

The rubber plug is identified in the above picture. It is in front of the main tower that contains your main Jet.

[oldyam80sg]

I will have to look again because i don't think i saw this plug but i could be wrong.I suspect the octy is leaking as i turned my Pingel petcocks to off and the bike still runs.I know that whatever is in the float bowls will take a while but after 7 to 10 minutes bike is still running.I took off float bowl #3 and the needle valve spring keepers were almost off the tang so i turned them around and reinstalled float bowl.Tomorrow i will look at eliminating the octy as i suspect that this is leaking.

[The Lorax]

I thought only the 78, and 79's had the plug. also being part of the reason that they had the bigger main jets. my 79 has 80 carbs and it does not have plugs in the carbs. I could be mistaken, would not be the first or last time. but I think the '80 did not have plugs over the idle jets. now someone who knows better than I please feel free to correct me if I are mistaken. also, make sure your needle valve is allowing fuel to flow as well as cutting it off when appropriate.

[oldyam80sg]

I don't think i have that plug either.I will look tomorrow.

[zookey]

We have a 79 and it has screws in the tops instead of rubber plugs as shown in the picture above.

[boyat68]

The key to the 80/81 carbs is the cross drilled pilot to main towers. Some 80s had the 79 carbs with brass floats and the towers were not cross drilled. My 80G had cross drilled pilot to mains with the rubber plugs in the pilot towers The fuel level was also raised as the float height was reduced to 23 mm thus raising the fuel height 2mm Some contributors to this site have successfully done without the rubber plugs while others have had problems. Since Yahama decided to put the plugs in the 80/81s, logic tells you that they intended to force the fuel for the pilots through the main jet. Since the mains were not able to supply the main tower untill the diaphragm assembly lifted and the greater vacuum funneled the fuel through the main allowing a greater volumn of fuel to take the bike above 4000 RPMs, thus cutting the flow through the Pilots.

[TopCatGr58]

Hey Boyat68,

I think you've got some confusing info here?

The early 78-79 carbs had the shared tunnels between the pilot and main jet tower, and had a screwed in plug for the pilot jet tower. It was designed this way to use the larger main jet as part of the metering function for the pilot, and fuel flowed thru the main jet, into the tunnel and into the pilot jet tower and eventually thru the pilot circuit.

In 80 they were changing the carb body style, the later 80-81 series carbs which do NOT have the shared pilot/main jet tunnel do NOT use the pilot jet tower rubber plugs. Each jet gets it's fuel directly from the bowl, neither sharing with each other, that's why they were able to reduce the main jet sizes down from the shared 137.5 to 110-115-120 range.

But...during the transition in carb body styles, they had some carb bodies that still had the shared tunnels, but the pilot jet towers were not threaded for the screw plugs, so they came up with the rubber plugs to prevent the pilots from getting direct fuel feed, since these bodies still had the shared tunnel, and so fuel needed to be routed thru the mains, and the sharing tunnel, and then to the pilot jet/circuit.

When the carb body transition was completed, and they used up the older parts, then the later 80 and 81 carbs didn't have the sharing tunnel, and do not need/use the rubber caps on the pilot towers.
T.C.

[boyat68]

The Technical Bullentin on most Parts sites contain the following:





Notice that the 81-83 models of the XS 1100 use the blind plug contained in the order kit of the Pilot Jets

[GNEPIG]

That is confusing isn't it?
Mikuni made carbs for several different bikes and the design was basically the same with small changes. In 1980 the carb design was changed alittle for the XS11 and it used brass floats and rubber plugs. But in mid/late 80 it changed again to the later design with the carbon floats and no plug over the idle jet and smaller main jets.
The Suzuki that used this this very simular design carb used the rubber plugs past 1980.
So when you purchase carb kits from different places, you get some extra parts to make sure your model carb has been covered.
OLDYAM, If your carbs have the little drain screw (have to use a screwdriver to open) with the nipple you have the later carbs.

[oldyam80sg]

No i looked today no rubber black plug and my float bowls have an actual bolt on the bottom no screw head.

[gearhead76]

Ok I have a 81 xs1100sh and I'm rebuilding the carbs I don't have rubber plugs I'm I suppose to or not. I'm Confused.