Emulsion Tube/Needle Jet specs

[meyekj]

Can anyone help me determine the correct emulsion tubes/needle jets for my BS34's? I picked up a set of three BS34's from a '77 XS750. From what I can tell, these carbs are the exact same as the BS34's that the XS400's used, but they are jetted differently. Figuring out what main and pilot jets I need was easy, but the XS400 manual I downloaded here calls out a "X-4" needle jet. I've searched here and googled this type of needle jet, but haven't had any luck. The needle jets that came in the XS750 carbs are stamped "Y-0." I understand that these jets also control lean or richness as well, so I want to start from the right, stock configuration. The carbs the PO owner put on my bike came from an 80's XS400, so I'm not sure they would even be the same if I pulled off the bike and took them apart.

Side note: I'm replacing the carbs because one of the float posts is broken, one of the main jets is completely stuck and I hate that the fuel mixture screws are recessed and not easily adjustable. Also I picked up the three XS750 carbs for $30.

I've got a '78 XS400 you can see in my profile. I have stock filters and "side pipe" exhaust that are baffled and probably just a bit more free flowing than stock (but that's just a guess).

Thanks for all of your help on this and for all of the great info on this site.

Kevin

 

[meyekj]

Because I know everyone loves photos, here's the latest picture of my bike. I've only made modest updates to date:

- drag bars
- flipped left mirror
- removed right mirror
- hand made seat
- rear tool "box"
- shortened turn signal stalks

It will get a smaller, bobber-type tail light, a new rear tire and cleaned and polished before spring.

 

[xschris]

These are the needle jets the xs400 used x6, x4, and 271 Y-2. They all look the same but have a different number. As long as you are using one of these you will be fine.

 

[meyekj]

Thanks XSChris! Any idea where I can find some? I can't seem to find any "x" 270/176 series or 271 needle jets any where. Thoughts?

Anyone?

 

[xschris]

What do the ones look like that are in it now?

 

[meyekj]

They "look" exactly the same as the ones in your photo and what are in my bike now, but from my research the letter and number designations denote the needle jet diameter.

Link #1

Link #2

The "X" version isn't represented on the chart, but if I read between the lines, X is smaller than Y and they each have corresponding needle diameters and tapers. If I interpolate the chart, X-4 would be 3.070mm.

 

[xschris]

If you have one of the styles shown in my pic you will be fine. What needle are you using the 78 had a 5Z1 needle set on the third clip.

 

[XSLeo]

Just use the parts out of the carbs that came on the bike. Those jets and needles worked once and can again.
Good price on the carbs.
Leo

 

[meyekj]

Thanks, guys. My math says there's only a 0.0012" difference between the Y-0 and the X-4 and 0.0008" difference between the Y-0 and the X-6. Regardless, I'm going to pull the carbs off my bike this week and see what's there. I should be able to make one of them work. Thanks, again.

 

[mike1990]

Where can I get a pair of one of the x6, x4, or Y-2 I just bent and chipped one. Been looking but can't seem to find a set.

 

[xschris]

I have a set of X-4's I can sell you for $25 shipped paypal only.

 

[mike1990]

Sounds good to me Chris. How do we get this rolling?

 

[xschris]

P.M. sent

 

[MartinMamrd]

Havent found other similiar post where emulsion tubes plays the main role, so..
from what i have read, I need not to care which noozle i have in my carb?
This guy seems to be an expert on XS400s (http://xs400.net/wb/media/faq_anhaenge/Vergaser_V1_2.pdf). He says that configuration is like that:
XS 400D - 142.5 main jet, emulsion tube X-4, needle 4th groove
other types: 13* main jet, emulsion tube X-6, needle 3rd groove
There should be a difference as all types uses 5z1 needle?
Have anyone tried to switch emulsion tubes (X-4/X-6) and leave other jets and settings as it is? How the bike behaved?

I got a repair kit for XS400D with 142.5 jet, but have x-6 emulsion tube and... my bike is running somehow, but its hard to start and it seems its lean at low rpms. It behaves like there is some air leak but there is definitely not. Yeah, one slide is slower than second one, but not that much (diaphragm ok).
When i rev it and the engine goes back to idle it almost dies, then after a while the idle is too high. Everything is stock and "by the book" except this emulsion tube. Any advice?