Octopus Mess!!!!

[dspshemp]

I have my bike running now, but it won't run when I push the choke all the way in, even after 10 minutes of warm up in warm reather. There is a hose running from the crankcase on the left side of the bike, and one that runs from the #2 intake boot. Which one of these is classified as the engine vaccum hose? I can't remember where I pulled which one from (it's been a while since it ran). It runs fine, but will not run without the choke all the way out. PLease help me again!!! Thanks a million!! RB

[chopper]

the hose from the left is for your vacum advance,it goes on to the head not the actual intake rubber. this is probably your problem..on an xs the inlet rubber shoul have a cap on,if not stick a screw tight into a short rubber pipe to plug the end,and use that to try it(the 4 pipes on the inlet rubbers are for carb synchronising)

[uk1.1s]

Octopus hell

Had the same problem a couple of months ago after a rebuild.

The vacuum advance goes into the intake stub on the carb body itself, as that has a smaller hole where it enters the carb - therefore damps the vacuum pulses as the engine runs.

If your set-up is like mine, with the 'octopus' then this is connected via the short hose to the inlet rubber manifold at number 2 carb. It sounds like chopper has the earlier set-up without the complication of the 'octopus' thing. I've just removed mine and re-plumbed the fuel lines. See an earlier thread if you want to do that - but if so, remember to block off the No. 2 vac intake on the manifold.

Get the the wrong way around (not recommended) and the vac advance unit tries to shake itself apart at idle speed and the vacuum supply to the 'octopus' (which controls the fuel) isn't really enough. If you can hear a loud 'chattering' coming from the left hand side of the crank, it's likely you have them wrong.

Not running with the choke all the way in could be that the bike is running very lean, so you may have an air leak.

- Are all the manifolds fitted tightly?

- Have all the vacuum intakes been plugged? (or have a pipe for the octopus - for carb manifold no 2).

- You could also check for cracks in the intake manifold. With the engine running, spray on some light oil - if an area on the manifold dries quickly then the oil is being sucked into small cracks (often not obvious). Sometimes accompanied by a change in the engine note as the oil stops air briefly. Cheap (semi-temporary) bodge repair is to tape around the manifolds with duct tape or electrical tape to block any cracks

Good luck

[chopper]

my mistake! i was not meaning to post bad info...i couldnt remember where the hose went (knew it was the inlet,couldnt remember if it was head or actuall carb,i knew it wasnt the inlet rubber) sorry for any confusion...oh and uk1.1 my bikes were the same as yours an 82 and 84 1.1s, now severely modified the reason i dont have an octopus is i run gravity feed now,different tank twin fuel taps etc hope i didnt cause too much confusion uk1.1 is spot on with the way to test for inlet leaks spray maintenance spray (wd40) all over the area you should hear the engine pick up revs if you are leaking

[Wayne]

Well I hope this helps.
I drew these a few months ago. We are working on a techtip for the Octopus for both the Standard and Special. Here are the images that show the octopus, in two different options, for your special.





Good luck with your bike.
Ride Safe.

[sixtysix]

Wayne,

Now that i look at those again, they don't actually show the octopus, just inline filters. The Octopus would actually be a vacuum operated 'manifold fitting'. Maybe I am looking at it wrong.

[xssiveone]

Gary, don't think you are looking at it wrong because I see, or maybe that's "don't see", the same thing. It looks to me like the octopus has been removed and replaced by the "y".

[uk1.1s]

Fuel line hell

Bit over complicated on the later XS / XJ IMHO.

My own experiments in junking the octopus have got as far as a T-piece on the vacuum supply from one of the inlet rubbers to feed the vac side of both both taps.

I then have simplified the fuel feed to the carbs by dropping a line down to the carbs - so that 1&2 are fed from the LHS tap and 3&4 from the RHS.

Stage 2 will be to put a 'T' in the fuel lines too so that both taps feed both sides of the bank of carbs. The reason for this being that as the tank gets near empty it's possible that I could end up with more fuel in one side than the other.

Some debate earlier about how low the fuel pipes go below the carbs and how this will effect flow. Unless I'm missing the obvious I always thought it didn't matter. Flow will always be delivered based upon the 'head of water (fuel)'. In other words, as long as the tank is a fixed height above the carbs the pipes could go to the ground and back and fuel pressure (therefore flow rate) will be the same. It's sorta like a syphon isn't it?

[dspshemp]

Thanks guys!! I had it right, just wanted to make sure!! Has anyone figured out any benefits or problems with removing the diaghragm assembly, and putting in Ts? The only advantages I see is easier troubleshooting/replacement, and no need to replace the diaghragm assembly if something goes wrong. Have there been problems with this? Please let me know. Thanks. RB

[chopper]

i only did it as when i changed the tank the taps were not vacum type.only disadvantage i can think of is filling the engine with fuel if a diaphragm leaks,but this wont happen unless your float needles are worn or poorly seated

[uk1.1s]

Getting rid of the octopus

Reason I got rid of mine was that I saw it as an unnecessary extra.

Also I was having some problems with some cylinders not firing after a rebuild I managed to cure this after doing a number of things, one of which was to get rid of the darn octopus thing.

As it's not easily servicable to renew the diaphragm in it and not possible to check it's condition I decided to do without one.

Rules out one more thing to go wrong in the system I suppose.

[nashville_bill]

The only problem with removing the "Octopus" is that you will have to turn ON and OFF the petcocks everytime you ride the bike. The automatic fuel shut off is the reason for the thing.

I decided to keep mine and, so far, have not had any problems with it other than it takes up a lot of room. I added fuel filters and there just isn't any room to spare and I have been afraid that the fuel hoses will kink and stop the flow where they make the sharp UP turn to connect to the petcocks. I just bought some stainless steel braided fuel line to install that won't kink.

I wish I could have found some petcocks that were vacuum operated, like my XS650 has, so I could do away with the mess and keep the automatic fuel shut off.

[uk1.1s]

Fuel taps

Bill,

By running a 'T-ed' vac line from one of the carb manifolds I connected up the vac side of the taps. My understanding was that these are vacuum taps in their own right and therefore no vac in = no fuel flow out.

Think I checked this out - but age is getting to my memory these days.

It should be right though, as thats why they have a prime setting too.

I will experiment when I am next in the garage - and try not to get too covered in fuel!!!

[chopper]

hi you are 100% right about the taps being vacum operated,inlet vacum opens then when the motor starts,prime is only to fill the float bowls.

[Pat Kelly]

I know this is an old thread but I just bought a Special.
The diagrams I see still have 137 feet of fuel and vacuum hoses.
Simplest would be to use manual petcocks with one hose each or...
for those that like the automatic shut-off, use Standard petcocks.
I've owned 6 bikes other than XS's and the XS is the first I've had with vac. petcocks. Up till now I've had no problem shutting the gas off myself and the bike will remind you if you forget to turn the gas back on.