Little brass tube in carb throat

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Lewes96
Posts: 171
Joined: 20 Nov 2016 20:22
Location: Lewes

Little brass tube in carb throat

Post 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
morini_tom
Posts: 920
Joined: 05 May 2006 13:47
Location: Northampton

Re: Little brass tube in carb throat

Post 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…
Lewes96
Posts: 171
Joined: 20 Nov 2016 20:22
Location: Lewes

Re: Little brass tube in carb throat

Post by Lewes96 »

See pic attached VHB25BS carb.
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morini_tom
Posts: 920
Joined: 05 May 2006 13:47
Location: Northampton

Re: Little brass tube in carb throat

Post 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
mbmm350s
Posts: 666
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: Little brass tube in carb throat

Post 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
Lewes96
Posts: 171
Joined: 20 Nov 2016 20:22
Location: Lewes

Re: Little brass tube in carb throat

Post 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?
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3potjohn
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Joined: 02 Jun 2007 13:58
Location: Devon

Re: Little brass tube in carb throat

Post 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
Lewes96
Posts: 171
Joined: 20 Nov 2016 20:22
Location: Lewes

Re: Little brass tube in carb throat

Post by Lewes96 »

Both holes clear. Just interested in the purpose of the tube and if some carbs had it while others didn’t?
mbmm350s
Posts: 666
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: Little brass tube in carb throat

Post 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
Lewes96
Posts: 171
Joined: 20 Nov 2016 20:22
Location: Lewes

Re: Little brass tube in carb throat

Post by Lewes96 »

Cheers, address on the way.
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