Page 1 of 1

NC30 Emulsion tube wear?

Posted: Sat May 25, 2019 6:50 am
by Vincent
Hi team, had a glance down inside the rear carbs today and had a bit of a WTF moment when I saw the insane amount of wear in the top of what I believe is the emulsion tube.
It looks like the needles have worn a bloody massive groove into the lip/side of the emulsion tube here, anyone seen it this bad before? I've been chasing low RPM fueling issues for ages, and while I've got it running pretty nicely, there's a persistent stutter around 3kRPM that I can't get rid of, and that gets worse when I richen the A/F screws.
I'm thinking it's probably extra fuel making it's way up into the carb because the emulsion tube is so worn. Both of these cylinders run rich, with the right one (top photo) noticeably worse.

Reckon it's time for new needles and emulsion tubes?


Image
Image

Re: NC30 Emulsion tube wear?

Posted: Sat May 25, 2019 11:16 am
by dirty30-2008
Hi Vincent.I probably am that "home mechanic" who like to have a go at anything before admitting I'm beat but..
The lips/groove that can be seen in your photos looks like it is meant to be there. Not something I have noticed before but the surfaces look like they are machined that way.I imagine at closed throttle the needle is low down in the emulsion tube and the lip allows the fuel that is drawn up around the needle to enter the carb body. May be totally wrong and will undoubtedly be corrected.....hopefully. That way we all learn . If anyone has their carbs on a bench please take a pic and we have a comparison

Best of luck.

Re: NC30 Emulsion tube wear?

Posted: Sun May 26, 2019 11:09 pm
by hunter
That's pretty common in well used carbs,
Yes time for some new one's.

Re: NC30 Emulsion tube wear?

Posted: Tue May 28, 2019 2:19 am
by Vincent
Had a chat with Rick O, and it's not the emulsion tubes that are worn, it's the brass insert in the carb body that isn't a replaceable service part! Has anybody had any luck removing/repairing this part?

Re: NC30 Emulsion tube wear?

Posted: Wed Oct 02, 2019 1:58 am
by fourfingers
Vincent, just came across your post, so just in case: that needle jet is not worn by the needle, donĀ“t worry. That cutout is the same in all my nc30 carbs.
Also, the needle jets are press fitted into the carb bodies, and can be replaced. Heating the carb bodies will help to press them out.
Cheers,
Emilio