Needle Jet Holder versions

I have two sets of 26's and one set of 28's. I've stripped them all down to the bear bones and have an assortment of jets etc.

Ther appear to be two slightly different designs of needle jet holders? This is the tube like piece into which the needle jet screws.

Can anyone help me identify which needle jet holder I should correctly use in my 28's, as they both "fit" just fine. One obviously allows a greater flow but which one is correct?

Thanks.

Geeesh Barney! WHAT 28s are you talking about? All the 26s use the same needle jet holders aka emulsion tubes aka main jet holders... The 28s? Not quite so simple as the early ones are a shade different and only work with the needle jets used in the early 28s while the late 28s (1978 Z1R type, plus 28 pumper types) use the same ones as in the 26s. You WILL find that some of them have different numbers of holes on the side but WILL fit exactly. When I swap them out, I try to match the holes on the sides as well as the type. The early VM28SC carbs used on the Z1 models didn't use an o-ring...

Hey WG. The 26's I have are both 1976 KZ900. The 28's I have are, I believe 1975. Sync adjusters on the outside of the carb bodies and air side idle screw, not gas screw.

I was going to drop the whole 26's emulsion tubes/needles and 115 needle jets into the 28's, with 117.5 pilot jets, to see if the 28's might give me a little more OOMPH? The original 28's needles are looking pretty sorry for themselves.

Wadya Thank?

"I was going to drop the whole 26's emulsion tubes/needles and 115 needle jets into the 28's, with 117.5 pilot jets, to see if the 28's might give me a little more OOMPH? The original 28's needles are looking pretty sorry for themselves."

You can't swap the emulsion tubes. The jet needles on the 28s are 5J9 and the 26s are 5DL31... they will swap but they perform so close it would hardly be worth the effort unless the 5J9 were chewed up badly. The needle jets are sized differently. A needle jet is the brass piece that is UNDER the emulsion tube; between the tube and venturi that sticks out of the venturi. Those will not swap I think because they have different badge numbers (that is, they are different styles) and the emulsion tubes probably won't swap...

If you want more "oomph" from the 28s, they are jetted quite rich for stock airbox/pipes and unless those things are modified, you will want to stick with stock jetting. Both the 28s and 26s you have will have #17.5 pilots (NOT 117.5) and the mains on the 26s are #115 and the 28s are #112.5 - You can swap mains if you like.

Thanks WG. I'll report back when I have some news.

WG, I DID end up swapping out the needles because the original 28's needles were a little chewed. I didn't touch the little brass bits (emulsion tubes?) that stick up into the venturi but I DID change out the 1" long brass tubes that carry the needle jets. Replacing the original 28's tubes with the cleaner/newer 26's tubes. I also put a small "o" ring in the equation to "seal" the new tubes where they screw into the small "towers". Not sure this was in any way necessary but it DID made me feel realy good, like a real engineer, breaking unexplored territory.

All seem to be functioning fine aside from the fact the bike's running like crap because of the dodgie head gasket I used (see posting in "Engine" section).

Jeff's got some #15 pilots on the way to me to replace the 17.5's in there now.

I'll update when she's back in the land of the living.