1979 xs 11 special jetting

[dewibp]

Stock exhaust & stock air cleaner now. What should all the jetting be and what part number imulsion tubes should I use? Also, should #2 & #3 be jetted one size larger than the outside cylinders? I have a multitude of carb parts and need to sort out the correct set up. thanks

[Do Lee]

Jetting

Stock 1979 XS1100SF as noted on service data sheet.

Carburetor - Mikuni / BS34-II / 3H3-00

Main Jet / Pilot Jet 137.5 / 42.5
Needle Jet / Jet Needle-Clip position X-2 / 5GZ6-3
Slide Cutaway or Throttle Valve 135
Float Level 25.7 +/- 1mm
Idle RPM 1100 rpm
CO% @ idle (Diagnostic Use Only) 3 +/-2%

Needle Jet, Main Nozzle or imusloin tube is an X-2 but parts list
shows different part # for carbs 1 & 4 (2H7-14941-02-00) and
(3H3-14941-02-00) for carbs 2 & 3. Both part # are X-2, 1 & 4
(2H7 Standard part #), 2 & 3 (3H3 Special part #). I have just
taken my carbs apart for repair and I can't see any differences
between the 1 & 4, 2 & 3 tubes.
All 4 carbs use the same jet sizes.

[dewibp]

Would you please count how many small holes (5) or (8) along the side of the tube? I think (along with Pro in Olympo) that the number of small holes impacts whether the two inside cylinders run richer or leaner. We believe this is the difference with part numbers. thanks in advance dew

[dewibp]

Blaine's XS 11 Carb FAQ thread page 9 states that emulsion tubes with less holes (small holes on sides) will make it richer (less air) and more holes with make it leaner. Pro from Olympo, what is your thoughts? How about anyone else too as I would like to confirm and save this information as I am getting up in age and don't remember too well anymore!

[TopCatGr58]

Hey Dew,

I concur with the more holes=leaner. I rebuilt a bank of 79SF carbs, and found the same difference, and I put the more holes tubes in the #1 and 4 positions, and the less holes in #2,3.

I think this was Yamaha's first attempt at trying to cool the center cylinders with slightly richer mixtures without using different sized main jets. In the later years, they started using the same emulsion tubes, but different mains, ie. 110, 120, 120, 110.
T.C.

[prometheus578]

"Holier than thou"

Checked several of my carbs for different main nozzles. I concur with T.C.... more holes on the outside, fewer holes in the middle two

[dewibp]

Thanks for the information all..... that is what I am going to go with.

[Shuriken]

Could mixing up the tubes create mid range problems? I.e., #1 and #2 lean and #3 #4 rich?

Wonder if in rebuilding I've mixed the tubes. I didn't look to see if they had the same number of holes...

Ben

[prometheus578]

"Inattention to details"

I didn't look to see if they had the same number of holes...

I never noticed either. I usually teardown only one carb at a time, but last week I also unbanked a set to soak and sandblast the bodies and saw the difference after all the parts were jumbled up together. As for performance differences... my rump is no longer sensitive enough to feel any if there were so I can't comment on that.

[John]

Re: "Inattention to details"

Originally posted by prometheus578
As for performance differences... my rump is no longer sensitive enough to feel any if there were so I can't comment on that.

You're not saying that you're a numb ass, are you?

[pit-fighter]

I just ran into the same thing while taking apart 2 sets of carbs to make one good set...I put the tube with less holes in all 4 carbs..thinking the po might have put the wrong tubes in...the bike runs good..but do you think i should pull the carbs and put the tubes with more holes back in the #1 #4 carbs...will it damage the engine to run it with the tubes with less holes in all 4 carbs?

[prometheus578]

"... the hole truth and nuttin' but the truth."

The whole hole thing was to help the inner two cylinders run cooler... not that it was more than a few degrees different in the first and second place. The hole bit was also for emissions, I believe, but only one of those diagnostic gizmos would ever know the difference. Not really too much difference between engines in most models, but they clowned with the emulsion tubes anyway. My 79F has all the same tubes. My79 special has the differing ones. This is a non-issue fer me, but I'm sure that someone will write and slap me around.

[GNEPIG]

no slap on the @ss for pro

.. pretty much what he said, i have switched those around in three different bikes with no ill effects or performance differences
i think you'll be" good to go"..................................at least to taco bell anyway................hmmm taco bell, got to go ....................