How to replace the emulsion tubes on a Mk1

[tdm850rider]

<!--quoteo(post=80289:date=Tue 22nd Apr 2008, 06:34 PM:name=92 3VD)-->QUOTE(92 3VD @ Tue 22nd Apr 2008, 06:34 PM) <{POST_SNAPBACK}><!--quotec-->Hello people, Randy here from the US.
A couple questions....Is the imulsion tube something that wears out, or was this replacement an aftermarket upgrade?
I've got a '92 3VD, and the carbs are starting to idle rough. I cleaned the pilot jets and it got (somewhat) better, but it's still popping and spitting at idle.
Will replacing the emulsion tubes restore performance, or is this just a precautionary thing? I've owned the bike for a few years now, but I'm just now getting to do some maintainence on it.
Also, what is the "official" name of the part on the microfiche? Part # would really help.

Any info on what to replace/adjust would help as well.
Thanks!
Randy<!--QuoteEnd--><!--QuoteEEnd-->
Hello Randy, Thomas here from the US...
The emulsion tube (brit name) is simply the tube that holds the <b>jet needle</b> in the carb.
What happens is the tubes wear from a round hole to an oval hole as the needle moves in and out.
Being a round needle in an oval hole you tend to get excess fuel leaking in past the sides.

There could be other reasons for the 'popping and spitting' (like air leaks in the carburator system).


If you look closely you can see the 'ovaling'
(The green inserted circles are perfectly round, you can see where both sides 'ovaled off' past the green.)

Replacing worn emulsion tubes will not only restore performance it will increase the fuel economy.

Definition of 'Emulsion Tubes' from the <i>Dictionary of Automotive Terms</i>:
<!--quoteo-->QUOTE<!--quotec--><b>Emulsion tube:</b>
Part of a fixed jet carburetor, in which air is introduced into the mixture through holes to help atomize it and correct excessive richness at higher engine speeds. A perforated tube which extends from an air bleed in the top of the air horn down into the main well. Admits air from the air bleed into the main well to emulsify the fuel in the main well. Improves idle response and stability when the engine is hot and prevents fuel percolation and general hot-starting problems. Also improves response in the main metering circuit during part throttle conditions. Also called main-well tube<!--QuoteEnd--><!--QuoteEEnd-->
<b>HTH</b>

This post was last modified: 23-04-2008, 12:01 AM by tdm850rider.