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Old 07-07-2019, 07:17 AM
probstct probstct is offline
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Join Date: Apr 2007
Location: Eau Claire, WI
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Fuel problems

I've had two different mech look and work on the bike.
When the petcocks are on the fuel runs and doesn't stop. The engine off.
I thought Iunderstood that fuel will not flow until there is vacuum. I want to ride. Please help, I hate to see her sit there!/
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  #2  
Old 07-07-2019, 08:32 AM
JeffH JeffH is offline
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Let's start with what did the mechanics supposedly work on?

~ Start with that. What exactly did they do.
~ Also clarify which XS11 we are talking about. Special or Standard? What year?
~ How long has the bike been sitting? When was it last ridden?

Then remove the oil filler cap and do the sniff test for gas. If you smell gasoline then an oil & filter change will be needed AFTER you fix the fuel leakage issue.

So from what you described the Petcocks are leaking. A petcock kit with new rubber and spring should fix that petcock weeping / flowing with no vacuum.

Then if you smell gas in the oil you have an issue with the Needle & Seats in the carbs. Even with some fuel coming out of one or both of the petcocks working needles and seats should keep the gas from flowing thru the carbs and into the cylinder and ultimately into the oil.

Give us more info then one of the gurus can give you some ideas of what to do next.

Jeff

BTW: if you don't have gas in the oil -AND- the carbs aren't flooded (a potential for a roaring fire) then there is no reason you can't ride the bike. That's why it would help us to know when the bike was last ridden. As long as float is not stuck and there is no gas in oil then I'd inspect it very carefully and maybe start it. Have fire extinguisher or hose available just for safety. Apparently there is no fuel leaking 'outside' the system anywhere (tank, petcock, fuel lines, carb T's or carbs)?
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78' XS1100 E
78' XS1100 E
78' XS1100 E

'73 Norton 850 Commando
'99 Triumph Sprint ST
'02 G-Wing GL1800

Last edited by JeffH; 07-07-2019 at 08:38 AM.
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  #3  
Old 07-07-2019, 09:43 AM
probstct probstct is offline
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Join Date: Apr 2007
Location: Eau Claire, WI
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It all started with me thinking I could rebuild the carbs, I got the bike running but could never get it smooth.
The first Mech put in K&N jet kit and air filter. Ran pretty good but not the best.

It sat for a short time, maybe a winter and then had another mech work on it to get it running. Got it home, barely, put it away for the winter. Tried to start it in the Spring, flooded out and ran the battery down and that was it for me. That was probably 2 years ago.

I love the bike, heritage, style, look and power. I just want to ride. Most people around here do not know the bike or will not work on it because it is too old.
1980 XS 1100 Special

I have put two rebuild kits into the petcocks and I'm curious if I had purchased the wrong ones. Do you have a source for the correct rebuild kits for the petcocks?

Removed the oil filler cap and I can smell fuel.
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Old 07-07-2019, 10:24 AM
JeffH JeffH is offline
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OK the bike is:

~ 1980 XS1100SG Special
~ Bike has been sitting for awhile maybe a year or two
~ Seems mechanics working on it a year or two ago made it worse
~ was running poorly last time it was running a couple seasons ago
~ Smell Gas in the Oil
~ Likely unknown K&N parts in Carbs since mechanic did it
~ Need Octy guru to help with petcocks and Octy
~ Seems helpful to you to get the actual recommended Parts & Part #'s and Source for Petcocks & Carbs


After the Petcock / Needle & Seat fuel issues are resolved the Oil and Oil Filter will need to be changed.
Any rust in the fuel tank?
Using any inline fuel filters?

Also, since the bike has been sitting it seems prudent to clean the Ground Connections. Battery to Frame Ground and Frame to Engine Ground. Just to make sure any poor grounds might be contributing to the poor running.

Let's see if a Special Guru has some tips & tricks to help you diagnose and fix the problems. I have Standards which don't have that Octy

Jeff
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78' XS1100 E
78' XS1100 E
78' XS1100 E

'73 Norton 850 Commando
'99 Triumph Sprint ST
'02 G-Wing GL1800

Last edited by JeffH; 07-07-2019 at 10:29 AM.
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  #5  
Old 07-07-2019, 11:00 AM
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dpotter58 dpotter58 is offline
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The needles and seats are a problem. Check to be sure the floats are not full of fuel and keeping them from rising to shut the fuel flow off.
Are your petcocks in run or prime position? If in prime, the fuel will flow regardless of vacuum or not.
If you're comfortable, pull the carbs, turn them up side down while blowing in the fuel line. If you can get air through, they aren't seating.
If you're not comfortable, get comfortable. Old bikes need home repair. You need to learn to work on them and there are plenty of folks on here that can walk you through any problem you find.
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  #6  
Old 07-07-2019, 11:17 AM
probstct probstct is offline
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Thank you both, JeffH & dpotter58!!
The petcocks are in the on position, not prime.
I am comfortable but, not confident.
I have removed the carbs and rebuilt them before I turned them over to the mechanic.
I will do what you say and get to this thread.
I believe that I have the Octy correct, I am going to replace the vacuum lines as to rule that out as well.
Thanks again.
do you know of a supplier for the rebuild kits with part number?
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Old 07-07-2019, 12:21 PM
JeffH JeffH is offline
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Some of us use Partzilla for OEM Parts (if they are available)
At least you can get the correct parts numbers for your 1980 SG

This should link you to the SG fiche
https://www.partzilla.com/catalog/ya...0sg/carburetor

Others may chime in with cheaper sources of SG Carb Parts THAT ACTUALLY WORK PROPERLY but at Partzilla fiche you can decide what you might want to buy.

BTW: here is the Petcock fiche for the 80 SG
https://www.partzilla.com/catalog/ya...el-cock-piping

I assume your 80SG is all stock and has not been molested or modified in the past.

many of us have bought Genuine Mikuni Carb Parts from JetRus www.jetsrus.com but I'm not sure they sell Genuine Mikuni parts for our bikes anymore:
https://www.jetsrus.com/carb_rebuild...it_mikuni.html

Keep us posted so we can help.
Good Luck

Jeff
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78' XS1100 E
78' XS1100 E
78' XS1100 E

'73 Norton 850 Commando
'99 Triumph Sprint ST
'02 G-Wing GL1800

Last edited by JeffH; 07-07-2019 at 12:30 PM.
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  #8  
Old 07-07-2019, 12:34 PM
probstct probstct is offline
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Thanks JeffH,
The bike is stock.
Thanks for the links, I'll get to work this week.
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  #9  
Old 07-07-2019, 03:32 PM
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skids skids is offline
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Quote:
Originally Posted by probstct View Post
Thanks JeffH,
The bike is stock.
Thanks for the links, I'll get to work this week.
K&N b
Rebuild kits have the wrong pilot jets. They are a different type than the Micunis. Be aware that the float settings (carbs upside down) are not the same as 78 and 79’s. Clymers manuel has a supplement for 80’s. Some rebuilt kits for the octopus have had issues. The fuel valves have an o-ring for the 80 carbs. The are notorious for failing and causing fuel to migrate into the crankcase.
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Down to two 1978 E's. Both stock air boxes with K&N filters, one with 81H pipes and carbs,
One with Jardine 4-1 pipes. 8500 feet elevation.
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  #10  
Old 07-12-2019, 04:51 PM
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jetmechmarty jetmechmarty is offline
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Your Special should have a vacuum shutoff valve mounted on the left carburetor. It is usually referred to as the octopus or spider valve. Unless it has been removed, fuel running with the petcocks ‘ON’ means that it is not closing or it leaks. There is a kit available for it, but be advised the o’ring in the kit is not thick enough to make a seal. You’ll need to replace it before completing the job.

Farther down stream, did anyone mention your floats could be hanging up? Some of the kits have float bowl gaskets the obstruct movement of the floats.
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  #11  
Old 07-13-2019, 05:47 PM
Bergman16 Bergman16 is offline
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A note from Len about his Octy rebuild kit—it worked for me:


VACUUM DIAPHRAM REPAIR KIT:

NOTE: there is an issue with some XJ700, XJ750-X, and XJ900 petcocks, and the XS/XJ1100 fuel distribution valve bodies where the o-ring seat for the diaphragm plunger was not drilled "straight" (perpendicular) to the mounting face for the diaphragm.......this is possibly why the original petcocks used a hollow o-ring, that would deform more easily to compensate for this (slight) mis-alignment situation......although this issue normally manifests itself as a drip-drip-drip type of leak, rather than a "pouring out" type of leak.

On the affected petcocks, we’ve found that it is necessary to slightly “lengthen” the plunger shaft distance, and the best way to do this is to use an appropriate sized deep-well socket, and place the plunger shaft/tip down into the well of the socket……so that the round metal disc will be sitting on the top of the socket opening, with the plunger shaft down inside the socket well.

Now, take a small hammer (or hammer-like object) and GENTLY tap on the tip of the shaft sitting above the disc, thus “dimpling” the disc in the center JUST SLIGHTLY and thus moving the plunger tip (with the o-ring) “closer” to the seat in the petcock body. This dimpling should BARELY make a concave surface out of the round. previously-flat disc.

As mentioned, some of these petcocks actually had their o-ring seat drilled slightly off-center (or cockeyed) in relation to the plunger shaft…….original plungers used a HOLLOW o-ring that could easily deform to make up for this slightly off-kilter orientation of the shaft vs. the seat. The replacement plungers use a standard, solid o-ring and this cannot deform as much as the original hollow o-rings do. By dimpling the support disc, and in effect “extending” the length of the plunger shaft, the solid o-ring can take up any tiny amount of slack caused by this non-alignment issue.
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'80 SG
"Fred" -- TC fuse box, stock airbox/exhaust/jets, SS brake lines, Windjammer V fairing, Cibie headlight lens, TKAT fork brace, Showa rear shocks, MikesXS emulators

Former bikes:

1973 Yamaha 125 Enduro (brother's but I 'borrowed' it a lot, usually after midnight)
1978 XS400E Red
1981 XS850 Special (Stingo)
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