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Little brass tube in carb throat

Posted: 01 Jul 2021 22:29
by Lewes96
Anyone know what the little brass tube slanting outwards in the bottom of the throat of the VHB carb? I have bought a new body and am fitting all the jets etc from the old one but finding this bit hard to remove. Just wondering how, and indeed what it is.
Cheers

Re: Little brass tube in carb throat

Posted: 03 Jul 2021 09:01
by morini_tom
Can you post a picture?

From your description it sounds like you’re taking about an extended atomiser, which is usually a 2 stroke carburettor thing…

Re: Little brass tube in carb throat

Posted: 03 Jul 2021 19:05
by Lewes96
See pic attached VHB25BS carb.

Re: Little brass tube in carb throat

Posted: 03 Jul 2021 21:47
by morini_tom
Oh yeah, that ones supposed to be there. I thought you meant pointing up protruding from where the atomiser meets the Venturi.

No idea how you’d get that out without damaging it. You’d have to check with fluid or air where the drilling goes but I suspect it feeds the idle/progression circuits.

If nobody here has experience of removing it, maybe eurocarb can advise? I’ve always found them to be very knowledgeable and helpful where dellortos are concerned

Re: Little brass tube in carb throat

Posted: 03 Jul 2021 22:54
by mbmm350s
It's called the air brake it can be removed but as it easy to clean on VHB(Z) carbs I have never needed to. It's purpose is to feed air into the atomizer if it is blocked the atomizer does not function correctly.
I don't think these are available as a spare part anymore.
Mark

Re: Little brass tube in carb throat

Posted: 04 Jul 2021 10:41
by Lewes96
Understood on the air feed to the atomiser. The existing body (being changed as the jet block split) has the pipe. The replacement has the passage but no tube (see pic). Just wondering if the lack of tube matters?

Re: Little brass tube in carb throat

Posted: 04 Jul 2021 13:37
by 3potjohn
Look up those holes with a torch , I would think you should see there is a “ pinhole” narrow brass fitting in both orifices one for pilot and one for atomiser. It is possible to just see the needle passing with a good light. A squirt of carb cleaner up each should appear if not blocked. A blocked one may respond to a carb wire or similar from a violin or guitar.
John

Re: Little brass tube in carb throat

Posted: 04 Jul 2021 21:26
by Lewes96
Both holes clear. Just interested in the purpose of the tube and if some carbs had it while others didn’t?

Re: Little brass tube in carb throat

Posted: 06 Jul 2021 17:07
by mbmm350s
Hi
>Just interested in the purpose of the tube and if some carbs had it while others didn’t?

Never seen a VHB or VHBZ without it, PHBH carbs are different.
I just removed one from a scrap carb, a little heat was needed- PM me your address and its yours.
The installed end has a chamfer for ease of installation
actually I removed two, the first one was bent...


Cheers
Mark

Re: Little brass tube in carb throat

Posted: 06 Jul 2021 20:32
by Lewes96
Cheers, address on the way.