Fuel lines

[leggman1]

Maybe I am trying to reinvent the wheel but why on earth did Yamaha create such a mess when they designed the fuel lines on my 81? I own a 78 BMW and its one line to one carb. Been working great for a zillion years. Can the vacuum valve be bypassed and just run from the petcock to the carbs? Whats the best way to do this. Dave

[motoman]

Maybe I am trying to reinvent the wheel but why on earth did Yamaha create such a mess when they designed the fuel lines on my 81? I own a 78 BMW and its one line to one carb. Been working great for a zillion years. Can the vacuum valve be bypassed and just run from the petcock to the carbs? Whats the best way to do this. Dave

Depends on whether your 81 is a Special or Standard.......sig. doesn't say.

[leggman1]

Sorry, Its a 81 xs1100 special

[motoman]

Well, in that case those extra lines and octy do kinda make for a cluster under there. Don't have that issue with the Standards.

[motoman]

BTW Leggman1, change that to an 81SH in your sig. Makes it easier for others to respond when you have issues. Lots of differences between the two....carbs,exhaust,rear tire size, etc.

[TopCatGr58]

Hey there Leggman,

I thought we had a tip about it, but just checked, and we don't!

Yes, you can remove the Octopus. The front spigots of the petcocks are just for the PRIME function, and can be either capped off with a viton/neoprene rubber cap, or you can "Y" the two outlets into 1 line,and then run it to the carbs. Best to run the lines from the left petcock to the right side carbs and vice versa to help run the lines without kinking. Also good to put on INLINE fuel filters. The Rear spigots are the RUN and OFF supply outlets.
The petcocks are GRAVITY feed, will flow without any vac. required. But this is where you really need to be sure your carbs float valve/seats are truly working and sealing. Otherwise you can do like Phil did an put on inline shut off valves between the petcocks and carbs so JUST in case the petcocks develop a leak, AND the carbs float valves also develop a leak, you can still prevent the flooding/fuel in oil scenario with the inline cutoff valves.....provided you remember to set them to off when you park overnight.

T.C.

[leggman1]

So if I got this right I can just run a hose from the front outlet on one side to the front outlet on the other side to block those off. Then go from the back outlet right side to the fuel inlet at the carbs left side and so on.
I have been shutting the fuel off on my bikes as long as I can remember just as a habit.
A simple vacuum cap should work at the manifold.
I have plenty of inline filters so that's not a problem either.
Thanks. Dave

[Aches n Pains]

I posted a picture of how I removed the Octy and added a fuel shutoff and additional filter for each of the two fuel lines. Works great and you don't have to worry about the petcocks dumping gas into the carbs if they fail. The link is:

http://www.xs11.com/forum/showthread...ht=fuel&page=2

[motoman]

So if I got this right I can just run a hose from the front outlet on one side to the front outlet on the other side to block those off. Then go from the back outlet right side to the fuel inlet at the carbs left side and so on.
I have been shutting the fuel off on my bikes as long as I can remember just as a habit.
A simple vacuum cap should work at the manifold.
I have plenty of inline filters so that's not a problem either.
Thanks. Dave

Also, be sure to cap off the two vacuum ports on #2 and #3 carb boots.
Use high quality rubber vacuum caps on those two ports, or they can easily pop off with a backfire and such.

[skids]

Also, be sure to cap off the two vacuum ports on #2 and #3 carb boots.
Use high quality rubber vacuum caps on those two ports, or they can easily pop off with a backfire and such.

And check them periodically because non OEM plugs may not hold-up to the heat.

[leggman1]

I am going to put some fuel in it in the morning and see if it will live once again. It has been ten years since it ran last but I went through the carbs and they were pretty much spotless. I did have to replace the rubber plugs but other than that it was very clean.
I am still working on the brakes but I should have that all sorted out in about a week. Just in time for winter.

[motoman]

And check them periodically because non OEM plugs may not hold-up to the heat.

Very true........but, if you use the black rubber thick walled ones from NAPA, they can easily be removed for carb sync,etc.
I actually have two new original ones from mother Yammy that came with the little spring clamp on them. Still in my tool box, as they weren't near as tight fitting as the NAPA ones, even though they are really thick walled. The NAPA ones are a really tight fit and need no spring clamp on them.

[leggman1]

Well I put the gas tank on it this morning and installed the fuel lines.
I was sure that I could put some fuel in it and it would fire right up.
Yeah right!
As soon as I dumped the gas in it started running out where the petcocks meet the tank. Not Good.
I did manage to get the lines off and remove the tank before a spark ignited the whole thing and burned down my house
After a little swearing and a lot of wiping up the spilled gas I managed to find a old riding mower gas tank and hung it from the ceiling over my bike.
It did start up and ran but it smoked a bit. Last week I dumped some marvel oil in the cylinders because the bike has sat for ten years and I didn't want to start it dry.
Once the marvel oil burned off the smoking almost stopped.
I did notice a small miss in the number three cylinder because The exhaust gas pressure from the exhaust didn't feel the same on the right as the left.
I did a compression check and had a good 160 pounds of pressure on ALL cylinders.
I am suspecting a clogged carburetor because even though the carbs were really clean the rubber plugs in the bowls were rotted out. Also all the new spark plugs looked brown except for the number three which still looked new.
When I had it running I pulled the plug wires one at a time and number three was the only one that didn't effect the idle speed.
I don't think its a spark issue because when I pulled the number three spark plug wire I could feel the spark running through me.
I will check the petcocks tonight to see if they are tight. Who knows what the PO did with the tank.
Bottom line is IT LIVES again.
Dave
There were mud dobbers in the old fuel lines so Maybe I didn't get all of that out.

[motoman]

Well I put the gas tank on it this morning and installed the fuel lines.
I was sure that I could put some fuel in it and it would fire right up.
Yeah right!
As soon as I dumped the gas in it started running out where the petcocks meet the tank. Not Good.
I did manage to get the lines off and remove the tank before a spark ignited the whole thing and burned down my house
After a little swearing and a lot of wiping up the spilled gas I managed to find a old riding mower gas tank and hung it from the ceiling over my bike.
It did start up and ran but it smoked a bit. Last week I dumped some marvel oil in the cylinders because the bike has sat for ten years and I didn't want to start it dry.
Once the marvel oil burned off the smoking almost stopped.
I did notice a small miss in the number three cylinder because The exhaust gas pressure from the exhaust didn't feel the same on the right as the left.
I did a compression check and had a good 160 pounds of pressure on ALL cylinders.
I am suspecting a clogged carburetor because even though the carbs were really clean the rubber plugs in the bowls were rotted out. Also all the new spark plugs looked brown except for the number three which still looked new.
When I had it running I pulled the plug wires one at a time and number three was the only one that didn't effect the idle speed.
I don't think its a spark issue because when I pulled the number three spark plug wire I could feel the spark running through me.
I will check the petcocks tonight to see if they are tight. Who knows what the PO did with the tank.
Bottom line is IT LIVES again.
Dave
There were mud dobbers in the old fuel lines so Maybe I didn't get all of that out.

For #3, I'd suggest you unscrew that sparkplug terminal from plug wire and cut that wire back a quarter inch. Re-screw the end back on wire and run it again.
If that completed the spark again, do the other three the same for grins'n'giggles.

[skids]

If you got a spark through your body, it may be a fuel delivery problem. You may want to see if the bowls have about the same amount of gas in them. Floats can stick (corrosion at the pivot pins), and also there may be a clog in the screen cap (if your carbs have those). This is a cap that snaps on to the carb inlet that can get gummed up with fule hose bits, rust, and whatever when there are no inline fuel filters.