80 & 81 carb discussion (not 78/79)

[GLoweVA]

Okay, I've started this thread to gather thoughts on what is really going on inside the 80/81 carbs.
Background: I've got my SG up and running (with some non mikuni pilots) and I'm running kinda rich on 3 out of 4 cylinders.
I've been trying to research the different parts that are in these 'new'er carbs. (not the 78/79 ones)

Research:
-The 80/81 carbs are BS34-111 and the SG,SH,LG,LH are 3J6-00 and the G is 3H5-00 and the H is 3H5-01. Nowhere on the carb bodies can anyone find these markings so trying to identify what carb body you have is almost impossible.
-They all have the same emulsion tube/nozzle (AKA needle jet) 300-X2 (part number 3H5-14941-02-00)
-They all have the same 42.5 pilot jets. (part number 256-14142-42-A0)
-The specials have different Needles 5GL-16 (part number 452-14116-16-00) that have no selectable positions clips
-The standard needles (G & H) 5IZ7 (part number 360-14116-07-00) have the 5 position clips and are almost unobtainium
-There's also the older/earlier 80 carbs that have the crossover drilled passage from the main to the pilot tower and thus they'll have the rubber plugs in the pilot holes.
-That leaves the Main Jets and the info here is contradicting.
The parts fiche and the manuals have larger mains listed for #2 & 3 for both the standards and the specials, but the numbers differ from 110's all the way to 125's depending on where you look.

Discussion/thoughts:
-The different carb bodies may only be differently number to reflect the different internals and they probably are all the same internally.
-The difference in the needles is that the G and H are more of a touring/highway type bike and thus needed a little different fuel mix while cruising, thus the different taper in the needles.
-For those that have the crossover passage, it has to draw its fuel from the main jet, thus the mains needs to be bigger on those carbs that have the pilot holes plugged.
-The Mains are a big hot topic for discussion because most have found that their bikes have all 4 the same. Some think that Yamaha decided that the inner cylinders needed to be a little more richer to help 'cool' them.

Some XSives have even swapped special carbs onto their standards and vice versa without a problem.
There are those out there that have varied their jetting from stock to support their different mods. (pods, pipes, etc.)

So, I leave this out there for all of those that have 80/81 carbs and please add your thoughts/experiences to this thread so that all of us can learn a little from each other.

[DGXSER]

OK George, I have been through about 6 different sets of XS11 carbs, 5 of them being the 80-81 type, 1 being the 80 style with the crossover. My thoughts and expereinces to your queries below;

-The 80/81 carbs are BS34-111 and the SG,SH,LG,LH are 3J6-00 and the G is 3H5-00 and the H is 3H5-01. Nowhere on the carb bodies can anyone find these markings so trying to identify what carb body you have is almost impossible.

This is true because the carb bodies were mfg by Mikuni not Yamaha, so they will not have a yamaha part number on them. The jetting and tuning is what may make them unique to the XS11 and its year or model.

-They all have the same emulsion tube/nozzle (AKA needle jet) 300-X2 (part number 3H5-14941-02-00)

True from what I have seen.

--They all have the same 42.5 pilot jets. (part number 256-14142-42-A0)

With the XSeption of the 78's this is true, in 78 they used 45 pilots with 210 pilot air jets in the inlets.

--The specials have different Needles 5GL-16 (part number 452-14116-16-00) that have no selectable positions clips

True, I have not seen a set of 80-81 style carbs, including the ones with the crossover, that have adjustable needles.

-The standard needles (G & H) 5IZ7 (part number 360-14116-07-00) have the 5 position clips and are almost unobtainium

No idea, not seen these.

--There's also the older/earlier 80 carbs that have the crossover drilled passage from the main to the pilot tower and thus they'll have the rubber plugs in the pilot holes.

Yes, have seen these once, and worked on them, but bike was destroyed before we got them tuned.

--That leaves the Main Jets and the info here is contradicting.
The parts fiche and the manuals have larger mains listed for #2 & 3 for both the standards and the specials, but the numbers differ from 110's all the way to 125's depending on where you look.

I have seen 120s in Steppenwolfs SG carbs, he has owned it since new. All I have ever worked on were same jetting across the board. Yes, the discussion has been that Mamayammie wanted to cool the inner cylinders due to lean conditions from detuning for emissions control by putting large jets in the middle carbs. Concensus has been that this was dropped by mid 1980 model year.

--For those that have the crossover passage, it has to draw its fuel from the main jet, thus the mains needs to be bigger on those carbs that have the pilot holes plugged.

Per Bikerphil, who has worked on these and achieved a tuned bike I am sure, the jetting and float height is the same as for all other 80-81 carbs. Boggles my mind why or how, but if Phil says it, I believe!

-Some XSives have even swapped special carbs onto their standards and vice versa without a problem.

Yes, I have swapped carbs from bike to bike and have a set of 78-79 carbs that I have had running decently well on my SH.

-There are those out there that have varied their jetting from stock to support their different mods. (pods, pipes, etc.)

Once I get a few more parts in, I may be learning this on my own with the SG I just got. From what I have seen to date with other members bikes here lcoally, it will all depend on what you have and how it is modded. Once you get away from factory pipes, there is such a huge diversity in what people are running it is impossible to standardize on jetting. MY SG for instance came to me with a Kerker 4-1 system. The baffles were shot and the internal baffling wrap material was long gone. It had been jetted and adjusted and it ran but not well. I know a local XSive DBeardslee has a 79F with PODs and 4-1 that he has running like a Swiss watch, not on the 80-81 carbs tough.

Hope that gives you some ideas to chew on.

[mack]

Mains

The mains were larger in the inner two for a while to mimic the 78/79 carbs in keeping the inner cyclinders cooler as was stated by Doug. The 78/79 carbs did it with two different emulsion tubes and same size mains. I would imagine that it was cheaper to produce main jets than emultion tubes so that was why they tried the config you point out.
All in all I've found the 80/81 carbs to be a mickey mouse production compared to the 78/79 carbs.

[GLoweVA]

This is exactly what I was hoping for when I wrote this thread.
Keep the info flying.

NOTE: This is for the 80/81 carbs only. NOT the 78/79 ones.

Edit: I believe the adjustable c clip needles were only for the 78/79 carbs and that I misspoke my info about the G's & H's having the adjustable clip.

[bikerphil]

There is one oddball type of early 80 carbs that came with brass floats instead of the plastic. Maybe these are the type that use the larger main jet size I have never seen a set of these in person though.

[motoman]

This is exactly what I was hoping for when I wrote this thread.
Keep the info flying.

NOTE: This is for the 80/81 carbs only. NOT the 78/79 ones.

Edit: I believe the adjustable c clip needles were only for the 78/79 carbs and that I misspoke my info about the G's & H's having the adjustable clip.

You were close..........81H had non adjustable needles.........cept for Canadian models........go figure. From a really old Yammy shop manual, 81SH stock had 110's across(lean&mean bar hopper), 81H stock had 115's outside cyls......120's center cyls. Some of that difference was due to the different configuration of the needles for both models, and for the 81H a richer main for the center two cyls. as it was considered to carry a heavier load majority of the time and the factory oil cooler restricted some of that upper air flow to top of cyl. head. Both models, and includes 80models had 42.5's for stock pilot. Don't know if jetting, needles,etc. were any different for the 80 'bastardized' carbs. My Venturer breathes thru 81Special carbs, 110's across, 42.5 pilots, stock air box/foamUniFilter, stock original exhaust, and stock gearing. When it's 'happy', 37-42mpg@70mph on a LD ride.......'back in the day' with somewhat 'real' fuel, two-up, 55-65mph(speed limit double-nickels), 46-52mpg was the norm on a LD trip.

[crazy steve]

-They all have the same emulsion tube/nozzle (AKA needle jet) 300-X2 (part number 3H5-14941-02-00)

-The different carb bodies may only be differently number to reflect the different internals and they probably are all the same internally.

I'm not so sure they all have the same needle jets (emulsion tubes), as I've seen different ones in different carbs. This is one place where I've never seen a definitive answer, and the service manual is no help. Keep in mind that checking the various parts fiches out there, they only show service parts, not always what was installed as OEM.

As to the carb bodies, you'll have different numbers for the LG/LH carbs due to finish (black), but I suspect that other than the oddball early-80 versions they probably are all the same.

[BA80]

[TopCatGr58]

I have an 81 SH and I can confirm that it came with 110's across all 4 stock!

Shortly after I got my bike "home" from Japan...in my ignorant youth, I quickly swapped out my pristine OEM/STOCK pipes for a set of JCW/Mac black ceramic 4-1's....for...ahem...improved performance!

I ran it 9 years with stock airbox, jetting, and the 4-1's, mostly local riding, but did a few LDR's....ie. Va. to Ft. Benning, GA and back, no problems, plenty of power to redline, think 30+ mpg, and never burned a hole in a piston.

Rebuilt topend with little 1179cc big bore kit, put on POD filters, so I upped my mains to 117.5's in all 4. I couldn't get a couple of the pilots out at the time...circa 2000...still a little ignorant mechanically and didn't know or try the special drilling techniques...so left the 42.5 pilots in. After break-in of topend, dyno run showed I could probably go up to 120's for a little better performance in the transition zone, pilot screws ~3 turns out works fine.

I have since successfully removed the buggered pilots, now have 45 pilot jets(mikuni), still works/performs fine..still 4-1's and Pods! Regrettably, only ~30-32 mpg at 65-70 mph!

T.C.

[CaptonZap]

The number of the carb was printed on the side of the bowl that the diaphram covered.
With a faint black ink. If the carbs have been cleaned with a good carb cleaner, the printing is gone.
The 80 G that has the originals is at another location, so I can't check, but if I remember right, the number was printed on the out side of the bowls as they sat on the bike. (the #1 and 2 were printed on the left side of the bowl, and 3 and 4 were on the right side).
It was very faint, and was readable with sunlight at the right angle.

CZ

[Schming]

Correct....

The number of the carb was printed on the side of the bowl that the diaphram covered.
With a faint black ink. If the carbs have been cleaned with a good carb cleaner, the printing is gone.
The 80 G that has the originals is at another location, so I can't check, but if I remember right, the number was printed on the out side of the bowls as they sat on the bike. (the #1 and 2 were printed on the left side of the bowl, and 3 and 4 were on the right side).
It was very faint, and was readable with sunlight at the right angle.

CZ

....as in this pic of my bank from an "E" :



...a 3J6-00 from an '80SG



It's real hard to see the numbers, let alone get a good pic, but they are there.
On the carb bodies on my stock '80G which has a MFG. Date of 6/79 they have 3H5-00 and the mains are 115 on 1&4 and 120 on 2&3 , next pic shows the drilled passage which gets the rubber plugs :




Next pic is the 51Z7 Jet needle that is from my '80G 3H5-00 carbs



Next pic shows the '80SG 3H6-00 carb with no drilled passage or plug and 110 mains in all 4

[motoman]

....as in this pic of my bank from an "E" :



...a 3J6-00 from an '80SG



It's real hard to see the numbers, let alone get a good pic, but they are there.
On the carb bodies on my stock '80G which has a MFG. Date of 6/79 they have 3H5-00 and the mains are 115 on 1&4 and 120 on 2&3 , next pic shows the drilled passage which gets the rubber plugs :




Next pic is the 51Z7 Jet needle that is from my '80G 3H5-00 carbs



Next pic shows the '80SG 3H6-00 carb with no drilled passage or plug and 110 mains in all 4

Appreciate the jetting confirmations T.C. and Schming............frustrating at times to be debated on stock jetting of a year model(s) I've been associated with since '81. BA80, that chart(which you've shown before) IS the most accurate.....cept for the 81Special main jetting, which IS wrong. That main jetting WILL work for the stock 81Special, just a bit rich till it gets wound up a bit, then hang on.......BTDT too!......but not practical for all-around good performance.

[ViperRon]

I have an original 1980 came with 115 and 120 mains always ran lean all cylinders even when new. Does not have the brass floats. Has the adjustable clip on needles and moving did not help much with lean mixture but did seem to change acceleration and make it less smooth. Now with Mukini 122 mains instlled clip in center floats set exact and all other jets normal it now has brownish yellow color on plugs, pipes do not blue down around the bottom bend, and the idle does not change drastically after a long run on a hot day like in the past.

However this is my bike and I am sure other models need different jettings.

[GLoweVA]

So what I've gathered thus far is, as long as the whole set has the right/same needles then the main jets should be anywhere from 110s to 120s depending on my particular needs.
Example, my G has an oil cooler, so that may restrict some airflow to the middle 2, so maybe go one size bigger there than the outer ones.
Whereas my SG has no cooler and then they should all be the same.
Now as to what size, that would depend on my mods. I've got K&N's in both airboxes and Mac mufflers on the G and stock mufflers on the SG.
So, I suppose I'll just have to pick a size, try them out and read some plugs/colortune and adjust up or down if needed.
Since both of my bikes are highway riders, I should tune them for the longer haul type driving that I do everyday, vice the sporty 'bar hopping' rides the specials were 'designed' for.

[natemoen]

Yamaha gave up on the staggered jets cause it really didn't do anything significant. Keep all the jets the same for simplicity sake.