Petcock

[Iron Duke]

I am the new owner, and new member here and am having a problem with the 1979 Yamaha XS1100 I bought from PO, I know the petcocks(2) are vacuum,I need to know where to leave the handle at. prime, reserve,or on I belive it should be to the on position all the time(save times that I have to prime carbs, or low on fuel. The XS I got was sort of a barn find with only 16000 miles on clock (was last taged in 94),put battery in her started her up, filled with petro and rode her home (81 miles)ran really good up to 70mph then started bogging down,did get her up to 90 at one time. PO put straight pipes on. Will be changing oil/filter,new cone fuel filters, and dumping a can of sea foam(will put 2oz of sea foam in crankcase before changing oil& running about 10-15 miles) in gas tank then running tell amost empty (has just shy of half tank now) whatya think? any suggestions are welcome. thanks the newbe

[CatatonicBug]

Congrats on the new aquisition! You lucked out being able to actually RIDE your new bike home. Most of us had to trailer them home and bring them back to life. You are correct about the petcocks. "On" is the proper setting, and the vacuum from the engine is what allows the fuel to start flowing (unless the vacuum diaphragm springs a leak). "Prime" bypasses the vacuum for when you are tuning things, or right after you have cleaned the carbs (and they are empty).

You may find that the straight pipes will cause nothing but a headache when it comes to tuning. These engines require some back-pressure from the pipes to run properly. That may be the only reason for your lack of power over 70mph.

If you don't have a manual yet, you can download one from the link in my signature. We like pictures too, so let us see what your new ride looks like!

Oh, BTW, this section of the forum is for instructions on hwo to use forum features.

[Iron Duke]

Petcock

Glad I got the setting right, thanks for the help. regards Duke

[natemoen]

DO NOT drive the bike with sea foam in the oil. Just let it warm up and idle with the sea foam in it. It thins the oil and depending on what else is going on inside the crank case you could spin a bearing.

[tinman905]

If you are putting Sea Foam in your engine just let it idle for a short period ,it's safer than riding it with that in your oil. Let the oil settle for ten minutes before you drain it . That will give lots of time for all the old oil to reach the pan .

If you are going to clean the carbs careful what carb cleaner you use if you don't completely disassemble the carbs .The seals can get damaged easily if you soak your carbs in a strong carb cleaner.

You might want to clean all your electrical plugs and ground. Using some dielectric grease on them is a good idea also ,especially all the plugs behind the fuse panel .That will save you some head aches in the future.

[Larrym]

Automatic Systems and Murphy's Law...

Iron Duke,

Awesome. Exciting. Congrat's on getting a bike with low miles and in "relatively" good shape. Frankly, I was just as excited when I got my first XS even though it had been abandoned for 4 years under a tree in the Pacific Northwest. Just didn't matter. It wasn't just a bike: Eeet was a SUPERBIKE, man!!!

Regarding those automatic "vacuum-operated" petcocks: They work great. Well...that is until they DON'T work so great. Lot's of threads with the phrase "Gas Flooding out of the Airbox" here on the site. Some fire recently where a member's bike went up in flames and took his house with it. (Can't recall if it was a fuel or electrical problem which was the source of the fire...)

No, I'm not an alarmist or even polarized against those automatic petcocks. Just saying that like all "automatic" systems/devices, it is the owner's/rider's responsibility to be mindful and diligent.

If ya have those automatic petcocks then before every ride prudence would suggest that you check the engine oil sight glass. Level too high??? Likely that the petcocks allowed gas to overflow and enter into the crankcase.

Automatic means that ya gotta check that they've done what they should before every ride. But then you already do a pre-ride check, right? Automatically???

(Kinda defeats the whole "Don't have to worry about it...it's Automatic.", IMO)

[Iron Duke]

Seafoam and carbs

Thanks Natenoen,Tinman,Larrym for the feed back. Know about those Vacuum petcocks as I also have an 80's Kawasaki that when I first got her had to change oil Twice, then went with the plate,and a pringle manual petcock(maybe the XS will get them to!) but as of now the OEM'S are working for me. Have used the Seafoam for couple a years fantastic stuff, has always done me right.Use it in the gas tank,and have used it once or twice in each bike, 2oz's in the tank every other fill up double that in the crankcase then around the block a couple of times (under 40)to mix thru, and get in to the plates while going thru the gears, one more oil change for the XS before winter with (one more time ) the 4 oz's of seafoam to finish off the cleaning of the inside of engine, then it will be 5K before I use the foam in the block again,again thanks Guys, and if ya think I need to know something let me know. Know my Kawi's,just learning the Yamaha's,and yes I have Owners and shop manuals on the way viva USPS. regards to all Duke

[bwilding_2000]

I am doing manual petcocks on my 79xs11sf. I want to keep the octy and install single tube manual petcocks. Top carb Ts are vents, the bottom Ts should take the fuel in. Do I split the lines from the tank to 1-2 on one side and 3-4 on the other ? I am a little confused now that it is all taken apart. What do I do with he factory inline Ts that are already in the lines?

[Incubus]

You rode your new bike home at speeds of up to 90 mph after it had not been tagged since 1994? Either you changed the tires before the ride or you should have used that luck buying lottery tickets.

There is only one thing you need to know about XS11 petcocks. They are the Devil's Work. Dastardly Evil. They can leak more gasoline than a BP Gulf oil rig.

Do a search on "I hate my petcocks" and you will see what I mean.

Good luck with your new ride. These are great old machines. I have two.

Patrick

[CatatonicBug]

I am doing manual petcocks on my 79xs11sf. I want to keep the octy and install single tube manual petcocks.

I'm not sure I understand what you are trying to accomplish. If you only have a single tube from the petcocks but retaining the plumbing of the octy, you will basically be bypassing the octy all the time, since it will automatically be on "Prime" all the time. You might as well just remove the octy if youare going with the single-tube petcocks.

[DGXSER]

Actually Bug, he COULD take the single outlet from the petcocks to the inlets of the octy and then from the octy to the fuel inlets. Eliminating the PRIME function.

Not my choise of operating parameters, but then, I have never enjoyed the octy. I wonder if this would still yield a reserve function though? That is one feature I'd hate to lose, its been of use on a few occasions and without it would have led to a long walk with a heavy date!!

[Iron Duke]

You rode your new bike home at speeds of up to 90 mph after it had not been tagged since 1994? Either you changed the tires before the ride or you should have used that luck buying lottery tickets.

There is only one thing you need to know about XS11 petcocks. They are the Devil's Work. Dastardly Evil. They can leak more gasoline than a BP Gulf oil rig.

Do a search on "I hate my petcocks" and you will see what I mean.

Good luck with your new ride. These are great old machines. I have two.

Patrick

Incubus, PO put tires on,thinking he was trying to get it up, and ran out of go, avon on back, bridgestone on ft.,new. starting price was over a K but market is more depressed now than i've ever seen it,had it listed for over a month,in the end he just wanted to be out from under it,been two months now have taken care of the problem she now will top out where stats say she should.like i said market depressed have had my KZ550 for sale for those two months,with just two bites, but no takers yet.Yes I believe in XS11's.

[Iron Duke]

Incubus, PO put tires on,thinking he was trying to get it up, and ran out of go, avon on back, bridgestone on ft.,new. starting price was over a K but market is more depressed now than i've ever seen it,had it listed for over a month,in the end he just wanted to be out from under it,been two months now have taken care of the problem she now will top out where stats say she should.like i said market depressed have had my KZ550 for sale for those two months,with just two bites, but no takers yet.Yes I believe in XS11's.

Incubus, Yes sir I know bout those vacuum petcocks, am watching like a hawk, so far thay have been 1oo%, (knock on wood) but I know someday it'll happen,and then my friend mr pringel,and mr backin plate will be needed.

[XS1100_OEM4ME]

Octy

I am doing manual petcocks on my 79xs11sf. I want to keep the octy and install single tube manual petcocks. Top carb Ts are vents, the bottom Ts should take the fuel in. Do I split the lines from the tank to 1-2 on one side and 3-4 on the other ? I am a little confused now that it is all taken apart. What do I do with he factory inline Ts that are already in the lines?

If you are going to go with single feed petcocks ie, on or off only, you can remove the prime fuel hoses (they are the ones that bypass the octy strait to carbs) then plum lines to the octy "in" on both sides then octy "out" to carbs on both sides. Down side, you can only prime carbs by adding vacume to octy manualy (can be done, even with your mouth, but a PITA) Next, If have a low fuel light and it works, it should come on about the time you would be needing resurve, so you shouldn't end up walking if you pay attention. Good luck with your bike