Mystery Carbs

[autotech44]

23MM for plastic floats, 25.7MM (1") for brass floats. Later carbs use plastic floats.

Thank you. They are plastic. I guess I have an older edition of the manual? And I'm assuming measurement should be to the top of the rounded part of the float, and not the squared off section which is higher?

[DEEBS11]

..........

[autotech44]

I know how to check level. It just makes no sense to not have a float height spec to start with. I've run into that before, and don't enjoy trial and error draining and pulling bowls.

[jetmechmarty]

I know how to check level. It just makes no sense to not have a float height spec to start with. I've run into that before, and don't enjoy trial and error draining and pulling bowls.

1981 carburetors got a drain nipple to connect the clear hose. Previous models did not. Use the 1980 float adjustment for plastic floats. Follow up check fuel level with the 1981 spec. All good.

[bikerphil]

Thank you. They are plastic. I guess I have an older edition of the manual? And I'm assuming measurement should be to the top of the rounded part of the float, and not the squared off section which is higher?

Measure from the flat...

[autotech44]

Measure from the flat...

What manual did that come out of?? Mine must be older with the brass floats.

[bikerphil]

Factory service manual.

[cajun31]

SUPPLEMENT 1980-1981 SERVICE INFORMATION.pdf. Here is the supplement you need. You will see that for 1981 because of the change of design in the carbs that the line level technique was implemented. Doesn't mean that the carbs don't function the same way the 80 models did. they are basically the same other than the float bowls and drains. Main thing is the floats are the same and can be measured the same as a way to set the float heights. I always adjust mine by the float height method on all my bikes. The line method is probably a better way but I just have not done mine that way. For your purposes the flats of the floats to the flat edge of the carb body with the gasket removed is how to measure them.

[autotech44]

It's PDF. They may have mixed the '81 supplements with the older XS1100E manual.

[autotech44]

Measure from the flat...

Does it stipulate check with carb upside down, or angled to just touch needle plunger?

[bikerphil]

Yes, carbs upside down, float bowl gasket removed.

[autotech44]

These carbs have been messed with everywhere. I noticed there wasn't much float travel. See the tab to prevent it from going too far when dry and pulling the needle out of the seat. I guess there's no spec, but it's supposed to be at 90 degrees.

[cajun31]

You are dealing with a mess that is for sure. Those tabs can only be bent back and forth so many times before they break off. I would probably apply some heat to it before trying to bend it back down. From what you can see are the seats and needles that bad to warrant doing that to the tabs? Who was it that worked on them? If you know, might want to ask why?

[cajun31]

It's PDF. They may have mixed the '81 supplements with the older XS1100E manual.

All the manuals from Yamaha started with the original 78E manual. They would alter it a bit or customize it for succeeding years and added in supplements as needed. Can be very confusing if you are not somewhat familiar with the model years. The supplement you have is strictly for the H or 81 year model. The reason I posted the pdf because it covers both 80 and 81. Not trying to confuse things. I know you are just working on an 81 but you had responded to Deebs post about the floats and the pdf I posted gives you both ways.

[autotech44]

You are dealing with a mess that is for sure. Those tabs can only be bent back and forth so many times before they break off. I would probably apply some heat to it before trying to bend it back down. From what you can see are the seats and needles that bad to warrant doing that to the tabs? Who was it that worked on them? If you know, might want to ask why?

It was two owner with little experience. The first did the Dynojet kit and drilled out the wrong plugs. The current owner tried jetting and adjusting float levels to fix the overflow, but never replaced the old degraded float valves.