Carb/octopus qiestopm

[bkush]

Hey everyone,

Need some help with the carbs on my XJ's. I have the service manual, and one bike doesn't have the "octopus" . I have lots of part, but only the one octopus. I have determined that the 4 numbered lines running off of it go to the petcocks, and one of each of those lines T's, but where does that other part of the T go? Also, the "octopus" has one other nipple on it. Where does it go?

My other bike looks like it was modified and doesn't use the octopus.

Any help greatly appreciated...

Bill

[newmaac]

Bill, the other line is a vacuum line that attaches to the vacuum nipple on the number 2 intake boot.
As to the routing of the 4 fuel lines, try looking under your seat. Originally, there was a fuel line digrahm on a sticker attached to the bottom of the seat pan.

This comes-up from time to time. There is a diagrahm that has been posted before. I did a quick search, but didn't find it yet.
I know it's there tho, if you are patient.
Good luck,

[Ken Talbot]

In OFF', nothing should flow from either petcock.

In ON or RES, fuel flows down hoses 1 and 4 to the octupus. It then flows from the octopus to the Ts on hoses 3 and 2, but only when there is engine vacuum to open the diaphragm. From these Ts, fuel continues to another set of Ts between the left or right pairs of carbs. ON draws fuel from the top of the filter stack, RES draws from the bottom of the filter stack.

In PRI, fuel flows via the petcock end of 2 and 3 to the Ts again, then down to the Ts between the carbs, entirely bypassing the octopus.

You test the operation of the diaphragm by disconnecting the vacuum supply from the motor and sucking on it either with your mouth or a vacuum pump.

Disconnect the hoses from the Ts between the carbs, use a couple of cans to catch any fuel, and test away.

[bkush]

Thanks for the help and diagram! Just what I needed! She's running like a striped-*ss ape now! WOW!!!!

Bill

[jazzrat2000]

won't start?

I was reading this, and it may have soimething to do with a problem I am having today...

I am a newbie to mechanics... today I replaced the valve cover gasket, and was feeling proud of myself until I got it all back together and tried to start it... no go! as far as I know there is only one thing I changed... I put the fuel lines back on the tank, turned the gas ON both sides, attached the gas warning light... but I found one of the two tubes that lead to the air filter from the carb area unhooked (the other was connected) and plugged it in like the other side was... could this have made it so gas cannot get to the engine somehow? the bike turns over great, I tried the choke(no help), but I don't want to run the battery down any more until I figure this out...

[Ken Talbot]

Have a look for a kinked fuel line (or two). With all that plumbing under the tank, it is very easy to do. DAMHIKIJD....

[Pat Kelly]

Did you hook the vacuum line to the diaphram back up?

[jazzrat2000]

no, but I am going to when I get everything back off to fix the leaking cam plug...

[don07tncav]

The fuel operates via the vaccume so you need to hook that up before starting. Mine is slow to start when I work on the carbs until the fuel gets back into the bowls. I put it in prime then try.

[scalded dog]

Question. Can you use the carbs off an 80 special, on an 80 standard, without using the octopus? TIA. Later 'Dog

[jetmechmarty]

Special carbs on standard

I think the carbs are identical. IIRC, the standard has vacuum petcocks, and the Special has the "octopus" instead.

[John]

Yeah, they'll work. I have 78 E carbs on my 80SG. Just make sure the main jets are correct.

[scalded dog]

Thanks, just wasn't sure. Later 'Dog

[TopCatGr58]

Hey there Scalded Dog,

Yes, you can use any carbs on any XS11, but the jets are set up differently. And it's surprising that the carbs are the same design in the same year, ie. 81, but the standard has 115-120 mains and the pilot jets are 42.5, whereas the the special has 110's straight across and 52.5 pilots. I don't know if the cams are different, or why they set them up that way? I'm suspecting that the richer pilots on the Specials are for more low end response or sportier in town response, vs. the leaner pilots but slightly richer mains for better mid range and top end needed for cruising and highway heavy load handling!?

So, you can use either combination. The trick is with the older carbs, you need to keep the same size 78-79 jets when using the 78-79 series carbs even when put on the 80-81 engine, and vice versa, if using the 80-81 carbs on earlier engines, keep the 80-81 jets in them!

The petcocks will provide the vacuum flow control to the carbs, so you don't need the octopus.
T.C.

[scalded dog]

Thanks TC, that answered another question I had. Later 'Dog