Hose question

[JJ]

Hello people of this great forum, I'm finishing the last bits to hopefully take my 79 xs1100 special for a first ride this week. I have a hose end up under the seat area that I'm not sure if its just a breather/vent or if it connects to something. I cant find anything searching here and online. The other end is connected to the top of the gearbox/trans area. Pic of hose attached. Thanks!

[jetmechmarty]

IIRC, that hose connects to the front of the airbox. It is a breather hose.

[Radioguylogs]

That hose is a vent for the middle gear case.

It is held in place under the gas tank by by a metal bracket, where it is protected from water.

It does not connect to anything.

Let me know if you need a picture.

[normalthom]

I'm getting ready to ride this spring myself and found something strange. The small metal tube was popping and spitting during warm up when I was messing with my 1981 1100 Midnight Special. The yellowish tube was just hanging there, so I assumed (now that seems incorrectly assumed) that it was supposed to be on that metal tube. The next time I was warming it up, I noticed that it had melted the tube like in the picture. Is that metal tube supposed to be exposed like that? Is the yellow hose just supposed to hang down?? Or is all of the hoses under there not in the correct places?? It runs pretty rough when it's cold, but once it's warmed up after about 10 minutes, it runs great. Thanks for any help you can provide.

[jetmechmarty]

Where is the other end of that tube going? That plastic tube is not OE.

[normalthom]

It goes into what looks like a breather box directly under the seat. I'll see if I can get another picture.

[DiverRay]

in your photo, the #2 carb boot does NOT have a plug on it! That WILL cause popping, as it's a big vacuum leak. That port should be connected to the octy. If you have removed the octy, it should be blocked like the #1 port. The line in the picture is wrong for the bike. If that is going to the octy, you need to replace it with vacuum line, not fuel line.

[normalthom]

Please forgive me for my inexperience. If you need a furnace, washer/dryer, refrigerator, microwave, or dishwasher fixed, I'm the guy. But with this stuff I'm lost. I had to google what an "octy" was and I still am at a loss.
octy - Urban Dictionary

https://www.urbandictionary.com › define › term=octy
A lame ass ****er who listens to his parents ****ing, not on purpose, but for fun. octi: "dude i only listen to that **** for fun, like if im bored and buzzed

[DiverRay]

The "octy" is what we call the vacuum valve that Yamaha put on the Specials. It used a vacuum operated shut-off to keep the gas from leaking if a carb float went bad. There are about eight hoses involved with it, hence the name. The petcocks have two nipples on each side, the front is prime, and rear is run/reserve, IIRC. The unit bolts to the carb support between #1&2 carbs. If your bike has fuel lines from the petcock to the carb "T", with nothing else it probably does NOT have the octy anymore. If that is the case, just block the port on the #2 carb boot. You can still buy the plugs from Yamaha, though they are like $12 for the four of them. If you do not know how old the plugs are, replace them all! they get hard and leak after a few years, and cause all kinds of problems trying to tune and sync the carbs.

[normalthom]

That's awesome!! I actually understand perfectly. Thanks for your help Ray. I'm hoping to ride my dream bike from my teens that I couldn't afford way back then!!!

[DiverRay]

Here is a link from this forum: https://xs11.club/forum/maintenance/...outing-diagram

[normalthom]

Ok, I played with my '81 XS1100LH yesterday and put a plug on the pipe that was popping. I found a plug from a yoder loop for an evaporator coil to a refrigerator and it fit perfectly. However, I'm not fully convinced that the yellow tube the melted when I put it on this same port a week or so ago shouldn't be on there. The third picture here shows the yellow tube on the right hand side of the bike and it's going to what looks like the same tube on that side. What am I doing wrong here? Once again, I can fix refrigerators, but I'm inept with motorcycles.
Also, I took her for a quick spin yesterday even though it's still pretty cold here in central Illinois and she seems to run pretty good.
Any help is sincerely appreciated.

[DiverRay]

That tube is not going to a stock Yamaha part! You would need to pull the tank and take a photo from above for me to try and figure out what it's for.

[normalthom]

Will do. Thanks Ray. If you look at the first pic, it appears to be some sort of filter that the back end is attached to. But I'll get some more pictures today.

[Radioguylogs]

Maybe a vacuum line for an aftermarket vacuum-actuated petcock?

If yes, then you are probably running on one petcock at the current time.