DIAPHRAGM ASS'Y For Fuel Lines Missing

[dbyers]

I have a 79 XS1100SF that runs okay but does need work. While looking over the bike I noticed that there was no reserve tubing connected to the fuel reserve/primary selector on the left or right side selector under the fuel tank. I got on Yamaha-motors and found that I am missing the DIAPHRAGM ASS'Y that the primary/reserve fuel lines hook to. It seems to sit on top of the carbs housing. It seems that the primary is the only one connected to the carbs providing fuel. Is this a problem? Can I buy a new replacement DIAPHRAGM ASS'Y or should I start beating EBAY for someone selling one. I also noticed that there is a smaller vaccum hose that connects somewhere that helps pull down the fuel on the DIAPHRAGM ASS'Y. I've checked the repair manual and it doesn't show where to connect it.

Thanks

[Dennyz]

The familiar name for what you are missing is the "Octopus". With out it, fuel pressure will always be on your float needles and my leak when on the side stand. Also, in the event of a lay-down, fuel will continue to flow with the engine turned off.

eBay would be a good place to look.
.

[rover]

Octopus

The way you described your lines, you will not have the reserve function. I have a 79 SF, and the octopus (the thing you are missing) leaked, so I removed it. There are two outlets on each petcock, and I ran a short hose to a Y (you could use a T, the Y seems like the flow will be smoother), from each of the petcock outlets, then to a bank of the carbs. Do this on each side. The SF can go 20 or 30 more miles on reserve, so this is a good feature to keep you from having to run out of fuel. If you do this, you will lose the shut-off function. That other small hose is a vacuum line, from the rubber manifold ahead of carb 2, and should be capped off if you go this route. A lot of guys, myself included, have gone this route, but there are a few drawbacks, as explained in the previous post, but I feel the octopus is a source of much trouble. However you decide is your choice. Good luck.

[dbyers]

Thanks

DennyZ and Rover Thanks for the help!!

[TopCatGr58]

Hey there Dbyers,

Rover's hot tonight!! Denny's right about the fuel still flowing if you lay the bike down, but "we" don't do that too often, do we?


When you stop the bike and park it, just turn the petcocks to OFF and you will relieve that pressure on the carb float valves! As Rover said, connect both petcock supply nipples to hoses, to a "Y" and then to the carb, that way you have reserve, which is a function of the petcock, NOT THE OCTOPUS!

BTW, that Reserve/"Primary" nipple is the "PRIME" nipple, it's purpose was to flow fuel directly to the carbs "Bypassing" the Octy, to get fuel into the bowls for starting!
Lots of us run without the Octy. Your choice!
T.C.

[Materi]

You can still get the diaphragm assy. (Octopus) from Yamaha. I did just that this spring to aid in the much discussed lake of fuel on the floor dilema which if you have not experienced yet, you soon will. Anyway I paid the Yamaha stealer 72 bones, installed it, re-hooked everything according to the clymers manual, and Voila...the very next morning the lake of fuel was ON THE FREAKIN FLOOR! So my fuel problem didn't stop until I installed new rubbers in the pet-cocks. As far as Dr. Ock...who the hell knows what his problem is, but he is not functioning as his Japanese desingers had so grandly envisioned 25 years ago . This winter I'm replacing all the fuel and vac lines, and we'll see what happens from there. Remember, be very cautious around open flame, electricity, and NEVER, NEVER smoke when approaching the bike until after you have re-built your pet-cocks Just trying to light-heartedly help a brother out.

Keith

[dbyers]

Thanks again for the help

Once again THANKS for all the help. This is my first street bike and I'm leaning a lot from reading and asking questions. I knew when I first decided on getting a street bike that I had to have a 1100SF. I'm 35 y/o and have alwalys loved the older Yamaha's. To add to the fun I'm only 5 foot 8in so touching the ground on my 1100SF is not exactly a flat footed experience. Thank God for tip-toes. To make matters even more interesting all my friends ride rocket bikes so I'm constantly getting jabbed for riding the 1100SF. I like the power of my bike but I am not into the speed. I'll take a winding mountain road doing the speed limit any day over 130MPH on the express way.
Don't know where I was going with that but again THANKS for all the help in answering my question...I'm sure I'll have more over time.

[dbyers]

Thanks again for the help

Once again THANKS for all the help. This is my first street bike and I'm leaning a lot from reading and asking questions. I knew when I first decided on getting a street bike that I had to have a 1100SF. I'm 35 y/o and have alwalys loved the older Yamaha's. To add to the fun I'm only 5 foot 8in so touching the ground on my 1100SF is not exactly a flat footed experience. Thank God for tip-toes. To make matters even more interesting all my friends ride rocket bikes so I'm constantly getting jabbed for riding the 1100SF. I like the power of my bike but I am not into the speed. I'll take a winding mountain road doing the speed limit any day over 130MPH on the express way.
Don't know where I was going with that but again THANKS for all the help in answering my question...I'm sure I'll have more over time.

[chevy45412001]

octypussie

i have one extra it is from an XJ,10 bones plus shipping if interested pm or e-mail chevy45412001@yahoo.com.Would recomend a rebuild though has been in storage for a while but is all in tack with the hoses on it.

[Buckb]

your post

I agree with TopCat. I don't run an octopus and I just turn it to off position. This is a good habit anyway since gas can run thru the carb and down into your oilpan if a float sticks.

We're close to you also (Cartersville) and we own 3 Xs1100s. Send me a private message and I'll give you our local contact info if you ever need help. Buck and Dee

[dbyers]

Guess what I found?

I called the old gentleman that I purchased the bike from and he gave me 3 huge boxes full of old xs11 special parts. I have to go through it and see what all I have. I hope to have enough extras to help out some other riders with parts if needed. The Octipus was there but I'm not sure I'm going to use it now.
Again thanks for all the help.

[jetmechmarty]

My petcocks flow freely in the on position. My XS650 shuts off until there is vacuum. Now I'm confused. Maybe my octopus is missing? What do I need to look for? If I forget to turn the petcocks to off, I sometimes smell gasoline in the garage.

[John]

The petcocks on the XS11 will flow in the on position. The XS650 uses a vacuum operated petcock that shouldn't flow unless the engine is running,or the petcock is in the prime position. It doesn't use an Octopus, and neither do I. I have a equalizer tube between the petcocks, and I only turn on on of them when I ride. That supplies plenty of fuel. If I'm going to be running at a high RPM, I'll open the other one then. If I'm not mistaken, both the on and reserve positions supply fuel to the same port on the petcock. I have the prime port capped off. You don't need it without an Octopus, anyway. Fuel will flow in the on position.

[jetmechmarty]

What is the "octopus" and what does it do? Why does the petcock have a "PRI" and "ON" position if both do the same thing?

Excuse my ignorance, but I've only ridden my SG. I got it with 10K on the clock last year. 16K trouble free miles so far. I'm sure the wrenching will come soon enough, so I'd better learn it.

[John]

The octopus is actually an on/off valve, and a fuel distribubution valve in one slick package that is controlled by vacuum. Fuel flows from the on port of the petcock (pc)to a port on the octo. From there it is routed to the carbs. The prime position will actually bypass the octo by using the other port on the pc and it is tied in to the fuel lines downstream of the octo, and directly to the carbs. The Standard uses different petcocks that are vacuum controlled, eliminating the need for the octo. The XJ11 uses the octo also. Why? I don't know, but I do know that you can live without it, but you will need to remember to turn off the fuel when parking the bike for a while. If you can repair a turbine, then this should be a piece of cake.