K&L Jet Controversy

[prometheus578]

"Holy Holes, Batman!"

Skids, I know what you mean by " 1,2 1,2. And I think I know what you mean by 2,2,2. Just another way of restating. If the jet was square... the BS30/96 (three hole) would have two holes on the top(with their corresponding two holes underneath), and one hole on the side(with it's corresponding hole on the other side)
When I refer to a three holed jet... There are actually six holes. The photo shows the three holed jets (which I contend are the correct ones)
The incorrect jet, the four holer, would have 2 holes per side(if square shaped), for a total of eight.

[prometheus578]

"The results are in... and it doesn't look good!"

Incredible... Just stinkin' incredible!
Just got back from Yamaha to pick up my "confirming" pilot jet. Yamaha had discontinued the pilot jets for the E,F,SF,G,LG,and LH, so there was no way I could order one of those to see what it looks like.
What I did order was a pilot jet for an SG,H, and SH. The old part number was superceded years ago and the new number was 4G0-14142-42-AO. I was not ready for what they gave me.
I'm handed an N151.067 series pilot jet. (small bore, no side holes)
I had not expected this at all. This clears nothing up!
Until someone can find an application guide from a carb manufacturer...
Or... people here need to check their machines and see just what's in them. Obviously, they must be stock. No high speed air filter systems or custom exhausts. No evidence that a previous owner stuck his claws in there and changed anything.
I have an "E", 2-"F"'s, an "SF", and I think an "H" in the shed. I will pop the bowls tonight and report what I find.

[mro]

The 80LG I got has a set of carbs which have not had the plug drilled out of them (yet)

If you want I could see whats in them.

Also, bought one carb kit from local YAM/KAW dealer.
Turned out to be a K & L kit (didn't use the jet)



mro

[prometheus578]

MRO... that plug covers the pilot screw. The PILOT JET is inside the float chamber... in the tower next to the main jet.
Your reply got me up and moving out to the garage. "What's he talkin' about...having a plug to remove?" All my carbs have an exposed screwhead that you can adjust the pilot needle with your fingers. Or do they?
I scamper about the garage and find four banks o' carbs. "Now ain't that a kick in the groin!" Two have exposed screwheads, and two have the recessed screws, (one already drilled). I really need to label my junk!.
Either way, my good slender screwdriver is at work so I'll just take these four with me in the morn, Identify what bikes they came from, and pop them open for a look-see.
(correction from earlier post: 3H5...have a "G" in the shed, not an "H")
Should be easy to ID, though complicated.
"E" and "F" have 137.5 mains, "G"s have 115/120's, "SG" has 110's
Starter jet: "E" #40, "F"#32.5, "G"+"SG" #25
I note that the "E", "F" and "SF" have carb BS 34-II, and that "G" and "SG" have carb BS 34-III.
Is the difference between the carb styles, amongst other things, the pilot screw being recessed under a plug, or the exposed, protruding pilot screw type?
(other than pushing the "G" in the shed, I've never messed with it... never noticed the carb difference till now!)

[GNEPIG]

.. of all the xs11 carbs that i have taken apart, newer and older, all of the pilot jets have been the same, what you call "3 hole type" and all have been 42.5s.. i have removed some strange ones from xs650 carbs and have received some stranger ones from K&L. but all of my stock pilots look the same

[prometheus578]

That's why I was so shocked when the pilot jet I ordered from Yamaha came back with NO holes. I'll find out for certain tomorrow, but I believe all mine are three holers. The Yamaha part# is discontinued for the bikes I have. I have no idea what was used later in the XS series. I doubt it was the "NO HOLER" that they shipped me, but the point behind this exercise was to find out.

[John]

Prom

You probably know this already, but didn't mention it. On the 80-81 carbs, the pilot jets have a direct feed from the bowl, vs the main jet feed for the pilot jets of the 78-79's. The older carbs will have a screw or a plug covering the access to the pilot jet. The newer carbs will not have anything covering the access to the pilots, as that is how they get their fuel feed. The older carbs will have the large headed pilot screws, and the newer ones are recessed, and capped over. The inlet side of the carb will have three holes on the edge of the air horn on the older carbs, and the newer ones will have four. The older carbs will have two sets of T fittings between # 1 & 2, and 3 & 4 carbs, the newer ones will have only two.

[mro]

the pilot screw being recessed under a plug, or the exposed, protruding pilot screw t

Sorry for not being a little more clear.

Meant that the carbs from the 80LG I have look like they have never been taken apart. Idle mixture are still plugged from factory.
(80 & 81?) to keep factory settings for emissions.

Could/should have original jets in there.


mro

[pggg]

Hey GNE, John, or Prom, I haven't owned any later model XS carbs, but being curious, do those carbs run an intermediate circuit in the transition between pilot and main? What does that extra circuit hole in the inlet rim do, and where does it go?

[John]

The extra hole in the inlet is the bowl vent. It replaced the hoses that were used on the older carbs. I don't think there are any intermediate circuit in them, it's just that the pilot jets get their fuel feed directly from the bowl, instead of through the main jet, and nozzle. The passage from main jet to pilot jet is not used in the newer carbs.

[TopCatGr58]

Hey Pggg,

A few years ago at one of the rallies, Rob Reil of Motorcyclecarbs.com gave a little class, along with handing out some info sheets. On it was an explanation and diagram about how the PILOT circuit continues to contribute to the fuel flow even after the primary circuit is activated by the vacuum slide rising! It diminishes as the vacuum level in the pilot circuit drops as the RPM's increase( I remember reading about that process somewhere here....Prom hath spoken it), and so I figure that's the way it handles the intermediate circuit process in both the older and newer carbs!?
T.C.

[prometheus578]

"I now know more than I should"

Carb Identification
Spent the last 5 hours sniffing green varnished gasoline.(and will be still smelling it in my nose for days) I've polished every jet with steel wool till I could read the numbers, and have scrubbed the numbering offa the sides of most of the vacuum chamber bowls trying to see what was stamped there. Here's what I've found.
'78 "E" model: BS34-II carb(2H7-00) Mainjet #137.5, Pilot jet #42.5 (three hole) Pilot air jet #180, Round brass float, screw over pilot jet, pilot needle pointed with exposed head, solid metal float needle, choke lever has plastic tip, external bowl vents.

'79 "F" model: BS34-II carb (2H7-10) Same as "E" model except for changed designation on vacuum chamber.

'79 SF model: BS34-II carb (3H3-00) Same as other BS34-II carbs 'cept different design of the bracket holding carbs #1 and #2 together at the vacuum caps. Also has a different designed choke lever, no plastic tip. (is this a "Special" thing?)

'80 "G" model: BS34-III carb (3H5-00)(different style carb)
Mainjets #115(carb 1+4)#120(carb 2+3) Pilot jet #42.5 (three hole),Pilot air jet #185, Plastic float, rubber plug over pilot jet, stepped pilot screw recessed into body, vitron tipped float needle, choke lever has plastic tip, carb bowl vents through airhorn(airhorn, inlet side has four holes instead of three like earlier models)

'80 "SG" model: BS34-III carb (3J6-00)
(I don't have one of these to look at, but research shows difference in that the main jet is #110) I can assume that everything else is the same as the "G" model, but I wont!

I have another bank of BS34-III carbs but it looks like someone's been in there. Has small bodied #130 main jets... doesn't look like they belong. (I have no idea what these carbs are for)

I need some help as I also have another bank of mystery carbs
BS34-II style, has 2H7 stamped on the outside, #137 main(not 137.5), pilot air jet in intake horn is #210, and the pilot jet, size unknown, is a FOUR HOLER! Any idea what this came offa? Or has this been dicked with?

These are the model carbs that I have. Anybody have any different readings for their carbs of the same make? Can other's post the info from their carbs for later years?

[TopCatGr58]

Hey Prom,

Well, I'm still recovering from having 2 teeth pulled today, finally stopped bleeding after 6 hours after the procedure! So... I haven't gone out into the garage to check the stamped #'s on the side of my carbs, but I can described what I found in them when I took them apart.

Plastic floats, 110 mains, 42.5 holes of 3 pilots, recessed pilot screws/caps drilled out, sorry-didn't check the air jet either, Viton tipped float needle, Plastic handled choke lever....it's SPECIAL

81SH owned since essentially new (15miles by PO in Japan)!

[prometheus578]

T.C., I included the pilot air jet numbers as they are readable, and are different for different models. Would help me identify makes of carbs that way, as they are not something usually changed.
Interesting that your special has a plastic tipped choke lever. My '79 special has a different design, more of a tab that sticks out the side, not up and is not plastic coated. Thought maybe it was a special thing for "Specials", guess not.

[TopCatGr58]

Hey Prom,

Perhaps your Choke handle had just gotten bent over and the plastic sleeve pulled off?? I've heard a few folks here mention that theirs looked like what you described! In my OEM owner's manual, it shows the plastic handle on both the Special and Standard's choke....IIRC!

Now that I've stopped bleeding , I can go out "tomorrow" and check on those air jets for you and the group!
T.C.