Mystery Carbs

[autotech44]

Hey all. Helping a friend with a 1981 XS1100LH. He's been messing with the carbs for years, and so did the guy before him.

Question #1

PODs and 4-1 exhaust. Where to jet. From what I've read 117.5 / 45. Or should I just up the mains x2 with a 115?

Question #2

Somebody replaced the pilot air jet. It's aftermarket 190. OEM should be 185. Parts diagram doesn't show it. And this aftermarket one might not look exactly what the Mikuni jet looked like. Where do I get the correct 185 pilot air?

Question#3

Needle jet is correct (X2) but looks a little corroded inside. Not sure if I should replace them. The needles are aftermarket with no markings (does dynojet have markings?). The specs show (see attached) correct needles are 5GL16. Yamaha part discontinued and can't find it anywhere. I guess I need the next best thing.

I'd really appreciate any input. Thank you.

[LAB3]

There's plenty of folks on the forum that'll help you better than I can when it comes to sorting out what's what when it comes to making it "right" parts wise. My take is for the amount of time, money and effort it might just make more sense to order up a new set of jets and needles in a Dyno Jet kit and be done with it

[Larrym]

Hey all. Helping a friend with a 1981 XS1100LH. He's been messing with the carbs for years, and so did the guy before him.

Question #1

PODs and 4-1 exhaust. Where to jet. From what I've read 117.5 / 45. Or should I just up the mains x2 with a 115?

Question #2

Somebody replaced the pilot air jet. It's aftermarket 190. OEM should be 185. Parts diagram doesn't show it. And this aftermarket one might not look exactly what the Mikuni jet looked like. Where do I get the correct 185 pilot air?

Question#3

Needle jet is correct (X2) but looks a little corroded inside. Not sure if I should replace them. The needles are aftermarket with no markings (does dynojet have markings?). The specs show (see attached) correct needles are 5GL16. Yamaha part discontinued and can't find it anywhere. I guess I need the next best thing.

I'd really appreciate any input. Thank you.

"He's been messing with the carbs for years, and so did the guy before him."

It's a sad but unfortunate and re-occurring situation you're in. ( •_•)

The real question is WHY as in how come the owner isn't happy with the way the bike is running. (O_o)

If it's that the bike just doesn't idle right after being warmed up? Spits and pops out the exhaust? Slow to accelerate from 1.5 K rpm up to 4.5 K rpm? (o_O)

Only pulls hard when past 4.5 K rpm so you gotta keep it in the high rpms for it to feel like a super-bike??? (•﹏•)

Then I'd say swapping Jets and needles ain't gonna fix it. (⇀‸↼‶)

Aftermarket carb kits (specifically float needles/seats...) on Amazon/Ebay with chinese/Ttaiwan parts were likely installed. (－‸ ლ)

No way that following the repair manual and just setting the float distance as "X- distance above the gasket surface" get the fuel to the right level. (；☉_☉)

Gotta set'em WET...



Provided you've ruled out the aforementioned float/fuel level situation? (O_o)

Go HERE for the jetting recommendations and find your individual set up-

https://xs11.club/forum/modifications/carburetors-fuel-system/394-jetting-recommendations#post394

Only place I've found the OEM AIR Idle jet is on an old set of carbs. NLA as far as I know.... (Θ︹Θ)

HTH....

[cajun31]

Hey all. Helping a friend with a 1981 XS1100LH. He's been messing with the carbs for years, and so did the guy before him.

Question #1

PODs and 4-1 exhaust. Where to jet. From what I've read 117.5 / 45. Or should I just up the mains x2 with a 115?

Question #2

Somebody replaced the pilot air jet. It's aftermarket 190. OEM should be 185. Parts diagram doesn't show it. And this aftermarket one might not look exactly what the Mikuni jet looked like. Where do I get the correct 185 pilot air?

Question#3

Needle jet is correct (X2) but looks a little corroded inside. Not sure if I should replace them. The needles are aftermarket with no markings (does dynojet have markings?). The specs show (see attached) correct needles are 5GL16. Yamaha part discontinued and can't find it anywhere. I guess I need the next best thing.

I'd really appreciate any input. Thank you.

Sounds like the cardinal rule of carburetors has already been violated so where to start. What you read concerning the jets is probably close based on what you have going on with the bike. 3 to 1 is about right. What kind of pods are they? have you verified the lip that mounts to the carbs is not blocking anything? One thing that is always stated and recommended is when making changes do 1 thing at a time. Like I said that is already out the window. Does your friend happen to still have all the original parts that were replaced? What parts are you dealing with now? Meaning are they original Mikuni or Ebay chinese junk? When you said needle are your referring to the actual needle or the emulsification tube it rides in? When you said a little corroded inside that makes be think you are referring to the actual tubes. If so they can be removed and cleaned. As for the air jets I don't have a good source for replacements. I did a quick search and found nothing. Others will chime in and give more recommendations.

[autotech44]

Don't know what real life symptoms were. Gas was gushing past every needle and seat. More gas than oil in the crankcase when I got it.

[jetmechmarty]

CV carburetors work better with the factory airbox. Some pods don’t work at all. As stated some pods block inputs into the carburetors. Uni pod filters work best with this BS34 carburetors.

For genuine Mikuni brass, these two vendors are good.

https://www.jetsrus.com/a_jets_by_carburetor_type/a_jet_kits_mikuni_selection.htm

https://www.nichecycle.com/categories/carburetor/mikuni-parts-by-category/jettting-tuning.html?srsltid=AfmBOooyWkw6jYldGgK5t7CAjxkq0RUVxxpf6ecFtE-0F_hCOsWYBYqk

[Larrym]

Don't know what real life symptoms were. Gas was gushing past every needle and seat. More gas than oil in the crankcase when I got it.

Yup.... That sounds about right. (＾◡＾)

I mean... the owner and the one previous likely did just what any reasonable and mechanically inclined person would do... clean the carbs and install new parts. (･‿･)

Sadly... those ebay/Amazon (Chinese/Taiwan) float needles and seats either don't regulate the fuel level at ALL resulting in flooding the crankcase... OR the fuel level is so far off the bike CAN'T run right. (ᗒᗣᗕ)

Thing is... the owner does exactly what he should- installs the parts, adjusts each one of them per the repair manual, and the bike runs like CARP! (╯•ᗣ•╰)

Then the true tragedy takes place as the owner starts chasing anything and everything ELSE that could even POSSIBLY be the problem-

Changing Jets, needles, COILS, new cam chain tensioner, pick up coils,.... a wild goose chase all over the bike EXCEPT for this float needle/seat problem. (●´⌓`●)

And in the end the owner is out of patience, money, and the bike STILL runs like carp so he bails on it to sell it to the next dude. =͟͟͞͞ =͟͟͞͞ ﾍ ( ´ Д `)ﾉ

I, myself had this happen to me. Not the wild goose chase of replacing/upgrading any and everything in a desperate attempt to get it to run right. (☉_☉)

Nope. I correctly determined the problem and got my superbike to run like it did BEFORE I installed those janky parts. (^_^)

I say start with making sure the fuel levels in the carb bowls is where it's s'posed to be and THEN look elsewhere. (⊙ᴗ⊙)

[jetmechmarty]

This carb guide may provide good info. It’s XS650 but it covers BS34 carburetors which both bikes share.
carbguide.pdf

[DEEBS11]

The XS11 Mikuni main jets are referred to as the "Large Round" type. The air jets are referred to as the "Small Round" type. This is the correct part.

https://www.ebay.com/itm/317880384493?_skw=N102.221-185&epid=171167201&itmmeta=01KNS4RVSRBC98VNCE9PF95VW3&hash=item4a0325bbed:g:E5UAAeSwT6hpkJ5W&itmprp=enc%3AAQALAAAA8GfYFPkwiKCW4ZNSs2u11xDceVg0NhqkxxAbWfhnNUHr3L1DGy7EGmKK3QNuzhyTkIbXETzJ641%2Bl3%2BTVImodXX%2BiPbiyQRq1%2Fq%2BQWO8IUEDPno4GlMMLiqLqDuLP2nFFgg21XI5AnQontuGeu4RVC%2BeDfyam%2FlxJE7x%2BUpnaV5MC0sZNxMuNgZmZD1GP2rXCBcdJVjg8ignUl8Si7HJpcIvoq4BbVuA9oe0eRNcsNm5TaWrtO1DG9bl0f3AiKFvOxxgHxReg%2Fg59zdAMI2nRDp9FpAD4d9f8%2Bl%2Bj8ysp27GmmYbg9ZsQTyDLBNoxTaqkA%3D%3D%7Ctkp%3ABk9SR6K946SuZw

[DEEBS11]

Stock 81 needles.

https://www.ebay.com/itm/277663006540

[DEEBS11]

XS11 #45 pilot jet.

https://www.ebay.com/itm/151075833851

[DEEBS11]

These are quality non-blocking (air jet) K&N air filters. I run all of this equipment that I just listed. Runs like fuel injection.

[DEEBS11]

117.5 main jets that you mentioned.

https://www.ebay.com/itm/358087364367?_skw=mikuni+genuine+117.5&epid=171222408&itmmeta=01KNS7TPVMJND65C1GFM87HM7E&hash=item535fab8f0f:g:9KMAAeSwe4Vpjhgt&itmprp=enc%3AAQALAAAA0GfYFPkwiKCW4ZNSs2u11xDDc5VL03Glge%2FIfunWF%2F17j0Z%2Fw22iNvvvho%2BA2SkHl0ndI8jAGWV%2FBfoElBxDrWdJHcNiob7X%2FsaL1lJ9oqvd9NHHVKdhW76oFvpuxEIrYAaXdohthlwfnj3ec1aLd5Myg0Il3FzNC5oNttgCSwfxD0JmyB5%2FhiiN2%2Bd2mpWGWYLhRWuUERqyjznz3Ayfxb%2F9nK%2FsUzLFDp3Dajxxns%2B%2FAB95hFTYNVQb%2F2Xxbehw6tO%2Fd3Z0kz%2B11bA3PCKEdeM%3D%7Ctkp%3ABk9SR47u6qeuZw

[autotech44]

Thank you. I think I figured out what happened. The previous owner installed a Dynojet kit, and the current owner replaced the pilot and main fuel jets. That explains the 190 pilot air and unmarked needles (with extra washer) that came with the kit. So my easiest fix should be going back to the Dynojet kit by installing the OEM 42.5 pilot fuel, and the Dynojet stage 3 main. The stage 3 main is DJ138, which going by a conversion chart equals a Mikuni 130. That seems very rich but maybe the other kit mods compensate. Has anyone had experience with Dynojet on this setup??

[DEEBS11]

I have installed many Dynojet kits over the years in Japanese and Harleys with success. I have not used one in an XS11. These days I like to only use genuine Mikuni or Keihin parts in modified carbs so you (the future mechanic) don't run into what you are going through now. BTW, I run K&N pods, Mac 2 into 2 header and my mains are 130s at sea level. Runs great.