Nylon Tube from Left Side Crankcase

[DJ48170]

Hi all. Newest member I think. I have a 1979 XS11 Midnight Special. Owned it for 3 years with no problems, until now. Just replaced the fuel lines because I leaked gas in garage.

Another problem created. What is the long thin tube going from the lower left side of the crankcase (?) up to the manifold? It looks to be nylon or neoprene like surgical tube, but it was old and brittle and just crumbled. How do I replace it and what is behind the rubber grommet on the back side of the Yamaha cover? Does the pic help? Okay, I haven't figured out how to imbed a picture.

[Montreux_Blue]

Vacuum advance hose.

[CatatonicBug]

Welcome to the forum! To clarify, there is no such thing as a '79 MNS. They were only made in '80 (XS1100LG) and '81 (XS1100LH). You may want to compare your Serial Number to this list, and put your model designation in your signature file.

That tube is a vacuum hose that controls the vacuum advance. Just get a new piece at any auto supply store. To post pictures, you have to upload them to another photo-hosting site, and link to them in your posts here. Here is a tutorial I created to walk you through the process.

[DJ48170]

Thanks for the speedy replies. I guess it shows what a novice I am. The Craigslist ad when I bought the bike called it a MNS, and who was I to argue. The first/last bike I owned (35 years ago) was a '72 CB350. LOL! A BIG step up, eh?

So I bought some vacuum hose at auto store, but do I have to take the cover off? Is there oil behind the cover. I am concerned a piece may have broken off inside.

[Montreux_Blue]

[Montreux_Blue]

No oil behind the cover.

[Montreux_Blue]

[DJ48170]

Yep, that's the hose I am talking about. Do I just stick the new hose in the rubber grommet or is there something that attaches to the other end inside the crankcase or whatever that part is where the Yamaha is printed?

What if there is a piece of old hose laying in there? What will happen?

[planedick]

Cover

Take off the cover, just 4 screws and everything will be very apparent. THE BEST thing you can do is get a manual and look it over real good. There's lots of things that need periodic attention and all must be done correctly or you will break something real bad.

[DJ48170]

Okay, what am I missing? Did you mean check my VIN to the list or a serial number that I don't have access to here at work?

[CatatonicBug]

Okay, what am I missing? Did you mean check my VIN to the list or a serial number that I don't have access to here at work?

Your VIN number IS your serial number.

[DJ48170]

Sage advice, Plane. I know there are more things that I could/should do, I am just trying to get it back on the road ... for the first time this summer. I will check behind the cover, and I WILL get a manual. Unfortunately I am my father's son, and we fixed (?) a lot of things based on "word of mouth" and I was just taking easy way (foolish) out for a quick fix.
I have recently found a local mechanic that specializes in older bikes that I will likely have do more complicated work. I am okay with changing the battery (done it twice so far) or things that are rather simple and obvious. I will NOT change tires, brakes, etc.
Again, thanks for reminding me of the pitfalls of "winging it".

[DJ48170]

Well then, my VIN does not show up on the list. In fact, it is not even close.

[Montreux_Blue]

This is what it looks like behind the side cover.

[DJ48170]

OMG Blue, you are amazing with the pictures!! Thanks sooo much! I picture really is worth a thousand words.

So does the vacuum advance line just push in there or does it connect onto some port in there?