What Size Jets?

[XJ Rob]

All four look to be the version III of the 80-81 model years, but there were some "bastardized" sets with all the newer looks, but still had the crossover in the tower and required the pilot jet to be plugged and jetted like the 78-79 carbs.

Not to be a PITA or beat a dead horse, but I'm just confused about what jets should be used. I took the carbs apart and looked in the "body" of the carbs and don't see any crossover from main to pilot jets. The Main "Nozzle" has holes in it and one big hole on the side in the screw threads. I don't see how fuel would get shared from the bowl. If pics help, I'll post them. Whatever helps to get this figured out.

I know the original needles were switched with adjustable ones. However, I don't know the correct spot for the little washer. Under the clip or above the clip. I'm not to impressed with the PO's work so I want to be sure. I should still be able to use them, I just need to find what setting is best.
Any advise would be great. I feel like the mechanic getting calls every day to see if their bike is ready. Don't get me wrong Dad is great but very impatient. Forgets sometimes I also have a life with things to do.
Again this is a 81 1100 Special, Stock airbox,K&N filter with aftermarket 4-1 exhaust.
Thanks

[CatatonicBug]

Pictures would definitely help.

[petejw]

hey Rob,
Personally id put every thing back to stock,
110mains and 42.5 piolot jets, needles in the middle position,
ride the bike and see how it goes.
The dyna jet kits comes with
124, 128 or 138 mains.
My bike rh(81) came with adj needles as stock, maybe the po
put those in, can you get a part no for the emulsion tube and
needle jet?

the needles length is 50mm
i know the dj needles are longer.

[XJ Rob]

Pics

I went out this morning and took some pics of the carbs. I hope things can be cleared up to get the right jets installed.









The top two small hole on pic 1 are bowl vents I believe.
The hole in the "Nozzle" (pic 3) is puzzling. Did they use older style even without a hole in the carb body?? I measured the needle and it measures 50mm

[dbeardslee]

Rob - On the pilot jet towers, no orifice between the main jet tower and the pilot jet tower simply means it's the later model carb bodies and you don't want to plug the pilot tower - just leave it open. That looks like an aftermarket slide needle - the stock ones are real pointy.

[XJ Rob]

Rob - On the pilot jet towers, no orifice between the main jet tower and the pilot jet tower simply means it's the later model carb bodies and you don't want to plug the pilot tower - just leave it open. That looks like an aftermarket slide needle - the stock ones are real pointy.

Well that problem is solved. (Keep the pilot tower unplugged.) Will the 125 main jets be too big? or should they be replaced with stock 110s?
Should the needles be replaced with stock ones OR can they be adjusted to work with whatever jets size I use?

[dbeardslee]

If the bike is stock - specifically the intake and exhaust - why would you want to go to bigger jets? I'd put it back to stock jetting.

[psycoreefer]

Again this is a 81 1100 Special, Stock airbox,K&N filter with aftermarket 4-1 exhaust.
Thanks

Uh, its not stock,

Id start with stock anyways, don't know where to go if you don't know where you started!

[dbeardslee]

Stock..With a few cosmetic changes.

Signature threw me . With a 4/1 and free flow filter, you're within' a couple jet sizes. If it was me I'd go two jet sizes bigger - 115's. 125's are six sizes bigger, and would be too much IMHO.

[XJ Rob]

With a 4/1 and free flow filter, you're within' a couple jet sizes. If it was me I'd go two jet sizes bigger - 115's. 125's are six sizes bigger, and would be too much IMHO.

Thanks dbeardslee,
What is your thought on the slide needle? Where does the washer belong? above or below the Clip? Thanks for the help. I greatly appreciate it.

I found jets at MikesXS part #48-0111 size 115. Will these fit the carbs I have?

[Incubus]

I don't know if what I offer has any value, but I'm not doing anything more important right now so....

My bike is a '79 with the older style carbs. I have, however, a K&N filter in the stock air box and an aftermarket 4-1 exhaust. I have stock jetting and my bike is a beast.

I just don't think that a K&N and a baffled 4-1 exhaust represent enough of a change to increase jet size. I would go back to stock and see how that works. You already know it's running way too rich. Dropping a couple jet sizes, IMHO, would not be enough.

I stayed with stock jetting when I rebuilt the carbs at the suggestion of my local Yamaha guy, who owns the shop and has worked on XS11s since he introduced the bikes to Austin when they first came out. He is an encyclopedia of these bikes. He suggested that a K&N and 4-1 would required shims on the needles, if anything. He was right.

Patrick

[dbeardslee]

It goes spring-washer-clip, and the little plastic thing goes on top of that. 9 times out of 10, assembly questions can be answered by a trip to the fiche. The fiche is your friend . I just looked up the 79 XS11 carbs (since that's the kind of slides you've got), blew the carb diagram up as big as it would go, and checked the descriptions underneath. That's where I got the answer. I've never compared a 78/79 slide with an 80/81. I assume the slides themselves are the same dimensions, but you know how you spell assume . I'm not sure that the center notch on the earlier needles is necessarily going to correspond to the 80/81's. I've got a disassembled 80/81 slide out in the garage. I'll go put it together, and measure from the tip of the needle to the bottom of the slide so you can compare it to yours - after a trip to the fiche to see how those puppies go together .

I found jets at MikesXS part #48-0111 size 115. Will these fit the carbs I have?

Yup. Dem's da ones .

I just don't think that a K&N and a baffled 4-1 exhaust represent enough of a change to increase jet size. I would go back to stock and see how that works. You already know it's running way too rich. Dropping a couple jet sizes, IMHO, would not be enough.

You really need to look at what the mods do with a colortune. Putting the mods on doesn't do a whole lot other than lean it out if you don't change the amount of fuel going into the chamber - it's sort of the point of doing the mods. Trust me - a couple jet sizes makes a difference.

[petejw]

Hi Rob,
looking at your pics, i know the emulsion tube is different,
mine has 10 holes in total. The needle looks longer but hard to
tell in the pics, how long is it?
Id go back to stock settings or i wouldnt go any bigger than
115 on the mains at this stage.

The pic of the carb bell, the 2 upper holes are float vents,
youve indicated the air jet correctly, and the hole on the bottom right allows
air to reach the emulsion tube.

[dbeardslee]

I found an 80/81 slide out in the mancave that was still assembled, so I just measured that one. 1.672 inches (sorry, don't have a metric caliper ) from the tip of the needle to the bottom of the slide. Keep in mind, those don't appear to be stock needles, so you may still have to play around with the setting.

[petejw]

..................
sorry doubled up on post