'79 XS project by a mechanical newbie. (But hey, it was free)

[skids]

2. Check the static height of the floats. I don't remember the exact setting for the '80, but it should be someplace close to 25mm, +- 2mm. Big thing is all 8 float sides are the same.

Unless he has a set of the transitional carbs, the setting for 80’s is much less than that. There are lots of threads on the subject if you do a search...

[bikerphil]

The later type carbs use a float setting of 23MM or 29/32".

[TopCatGr58]

I am having issues with fuel flowing into the carbs. When I hook up the fuel line to my tank with plenty of gas in it, it looks like a marginal amount trickles, then it stops with an air bubble still visible.

Turning over the bike does not pull fuel in as I had hoped. I pulled the plug on the outside of #1 carb and no fuel came out, so I assume there is none in the bowls.

Hey Stone,

SKids already covered the 80 float height of 23mm. The carb bowl vent is built into the carb and is the 4th small round port on the intake bell.

Okay, took the INTERNAL parts of carbs out and dunked/soaked, I'm assuming you meant the floats/main and pilot jets and jet needle. How about the float needle SEATS? And on the underside of the seat is a small screen that helps filter fuel coming into the carb body, can get clogged.

Also, did you spritz cleaner into the fuel inlet T fittings between each of the 2 carbs? Those can sometimes corrode/gum up and get clogged and prevent fuel flow, but unless you took the carb bank apart, you wouldn't necessarily pull the "T" out, and it has a fairly large hole so wouldn't suspect it to get clogged, but they can.

Also, rebuilt your petcocks, did you test the fuel flow from them NOT connected to the carbs, are they truly free flowing? The petcock screens in the tank can get clogged. Also the fuel gas cap vent can get clogged, and that can cause a vacuum in the tank not letting fuel then get out of the petcocks!

And like DIVERRay said, the vacuum advance hose goes to the #2 carb BODY nipple, NOT the intake boot nipple.

T.C.

[stoneairsoft]

Ugh. Just finished some summer courses for my masters and have a bit of time to tinker.

NONE of my float seats have filters on them. They all look like the upper right corner picture in Blaine's Carb FAQs, but do not have the filter portion on the bottom. They are not visible by looking in where the needle used to be. I assume the opening is too small for the screens to somehow get lodged down in the carb?! They have definitely not been on since I've worked on the bike.

The pilot jet isn't supposed to have a hole on the bottom, is it? Mine is a 42.5 6 hole variant with the hole on top where the screwdriver is inserted.


I only took carbs 3-4 apart from each other when Schming worked on a float post for me, but I don't recall cleaning the T at all.
I can confirm that the repaired float post is not perfect, and the float seems to be rubbing against the side of the carb when I hold it upside down. I know I measured the float heights...but I seem to have missed one. Setting float heights without a stand and extra hose for mounting on the bottoms of the carbs seems like a chore, but I'll try cleaning all the parts again and hope for a miracle. Are all the jets supposed to be seated tightly with the exception of the idle screw? I assume so.

I can confirm flow is GOOD from the petcocks. I ended up with a gush of gas all over when I put my fuel hose on the front nipple of the tank. (oops)

Vacuum hose is in the correct spot now.



Almost at 200 posts. Thank you so much to all who have helped along this frustrating and cumbersome road.

Hey Stone,

SKids already covered the 80 float height of 23mm. The carb bowl vent is built into the carb and is the 4th small round port on the intake bell.

Okay, took the INTERNAL parts of carbs out and dunked/soaked, I'm assuming you meant the floats/main and pilot jets and jet needle. How about the float needle SEATS? And on the underside of the seat is a small screen that helps filter fuel coming into the carb body, can get clogged.

Also, did you spritz cleaner into the fuel inlet T fittings between each of the 2 carbs? Those can sometimes corrode/gum up and get clogged and prevent fuel flow, but unless you took the carb bank apart, you wouldn't necessarily pull the "T" out, and it has a fairly large hole so wouldn't suspect it to get clogged, but they can.

Also, rebuilt your petcocks, did you test the fuel flow from them NOT connected to the carbs, are they truly free flowing? The petcock screens in the tank can get clogged. Also the fuel gas cap vent can get clogged, and that can cause a vacuum in the tank not letting fuel then get out of the petcocks!

And like DIVERRay said, the vacuum advance hose goes to the #2 carb BODY nipple, NOT the intake boot nipple.

T.C.

[TopCatGr58]

Hey Stone,


The float needle seat in the upper right of this photo HAS the filter screen ON the end of the seat!

The pilot jets ARE supposed to have holes in the pointy ENDS of the jets. The way the carbs are designed, the side holes are actually not important because NO air can get to them from the Pilot Jet tower, there are NO air ports to that part, the jet seats against the bottom of the tower and the fuel goes THRU the pointy end from the threaded end hole from the float bowl...UNLESS you have those rare bastardized transition 80 carbs that have a port between the MAIN jet tower and the Pilot jet tower. THEN the fuel comes from the MAIN jet, and the pilot jet towers are rubber capped off, providing the Main Jet NEEDLE/emulsion tube also has the hole/port on the the screw end to ALLOW the fuel from the main jet tower to the pilot jet tower. IF your main jet Needle/emulsion tubes DON'T have the port, then the pilot jet does feed directly from the float bowl and does NOT use the rubber caps on the towers.

Here's the sliced view of the 80 carbs:




Note NO tunnel between the main/pilot jet tower, and NO tunnels/ports to the side of the PILOT JET towers=NO VENTING for the jet side holes=not important.

Here are the 78-79 carbs:




NOTE the tunnel between main and pilot jet tower marked with red wire. The Pilot jet VENT occurs/joins in the pilot jet flow path AFTER the pilot jet chamber, that's where the air gets mixed with the already metered fuel, then it's further metered by the Pilot SCREW on the top of the carb body.

Photos are on Photobucket, viewable with the photobucket ADD ON for Firefox and I think Chrome might have one also! Hope you can see them!?

T.C.

[stoneairsoft]

Thanks TC. I'll re-examine/re read tomorrow. I still have to measure float height with more accuracy than a tape measure.

If only I could buy a Fuel Injection conversion kit



I can confirm those are my pilot needle seats, but they simply don't have the filter attached. I'll also upload a pic for you to see.

[stoneairsoft]

There is no pilot cap screw for the '80s carbs, is there? Because there are definitely none. The pilot jets are exposed for easy retrieval with a screwdriver.

I was able to use compressed air to blow the crud out of the jet on the left, but the one on the right, and one more both required dunking in carb cleaner for an hour, which did clean them out. I'm hoping this was a potential BIG problem stopping fuel flow.





Below is a picture of my float needle and seats with no screens, though I see there is a lip that could have been used to attach one at one point.

[bikerphil]

If the pilot jet is clogged at the end like in the pic above, that carb wont function below 3K RPM.

Yes, the screen for the fuel seat goes on that lip, good luck finding any. AFAIK, they are NLA.

[Radioguylogs]

...good luck finding any. AFAIK, they are NLA.

Not impossible, though:

https://www.mikesxs.net/catalog/prod...er/category/2/

[skids]

Forget about those inlet screens and change out your fuel hoses for new and use inline filters.

[stoneairsoft]

I do have nice in-lines installed, though I did remove them when these problems arose.
I will recheck floats as best I can, put pilot jets back & try her again in the next day or three.

[Schming]

There is no pilot cap screw for the '80s carbs, is there? Because there are definitely none. The pilot jets are exposed for easy retrieval with a screwdriver.

The fifth pic down in this thread shows the passage from the main to the pilot tower. The later carbs get a rubber plug in the pilot tower.



http://www.xs11.com/forum/showthread.php?t=35964

[skids]

The fifth pic down in this thread shows the passage from the main to the pilot tower. The later carbs get a rubber plug in the pilot tower.

Yes, the later carbs get the rubber plug only is the passage exists between the main and pilot bores. I have never owned a set of those “transitional” carbs, but I would bet that the pilot bore is not threaded for a cap and therefore a rubber plug is needed... Those carbs have been a challenge for xs11 owners!

[TopCatGr58]

Hey Stone,

Glad you found the clogged pilot jets and got them cleared.

You didn't say whether you found a sharing tunnel between the pilot jet and main jet tower?? If there isn't one, then YES, the pilot jet towers are OPEN, uncapped so they can feed from the float bowl, but with those clogged pilot jets, they weren't able to feed the pilot circuit, and like was said, you were only getting fuel when the rpms got up to and above 3k where the MAINs kick in.

Your float needle seat O-ring looks a bit flat, don't know how old they are, you may want to look at getting new ones to ensure you don't get any leaks around the seats which could lead to excessive flooding!

Keep at it.

T.C.

[stoneairsoft]

The float needle rings are definitely worn and probably doing little to no good right now...however, it seems flooding is not my main concern as getting fuel flow is......for now. But thank you for pointing that out.

I have not specifically looked for an adjoining passage, but I do not think there is one.

I will double check when I take the bank back off to look at carb #1...the only cylinder not firing.

https://youtu.be/c7N01mGIxQU

(The pipes did not heat up that fast...this was after a couple of start-ups)

I know it "runs" rough here, but at least it is giving me signs of hope.