Amal carb balance tube

SteveBorland · Sep 16, 2024

While chasing a mysterious lean condition on the Commando, I decided to change the carb balance tube. The one I have on is, I think, a left over from a Honda from many years ago. I have a spare from Andover, 06.2284, so I tried that.
It's almost impossible to get it on the stubs on the manifolds - is it supposed to be so tight? It's listed as having a 3/16" id, so I tried a 4.8mm hose I have - similar result.
I'll try again after warming it up, but it seems to be so wrong.

Triton Thrasher · Sep 16, 2024

Measure the outside diameter of the stub you’re trying to push a 4.8 mm hose onto.

concours · Sep 16, 2024

SteveBorland said:
While chasing a mysterious lean condition on the Commando, I decided to change the carb balance tube. The one I have on is, I think, a left over from a Honda from many years ago. I have a spare from Andover, 06.2284, so I tried that.
It's almost impossible to get it on the stubs on the manifolds - is it supposed to be so tight? It's listed as having a 3/16" id, so I tried a 4.8mm hose I have - similar result.
I'll try again after warming it up, but it seems to be so wrong.

Use contact cement for lube.
Then it won't pop off when the engine coughs.

Never had any trouble fitting 3/16 vacuum hose.

Amazon.com

marshg246 · Sep 16, 2024

SteveBorland said:
While chasing a mysterious lean condition on the Commando, I decided to change the carb balance tube. The one I have on is, I think, a left over from a Honda from many years ago. I have a spare from Andover, 06.2284, so I tried that.
It's almost impossible to get it on the stubs on the manifolds - is it supposed to be so tight? It's listed as having a 3/16" id, so I tried a 4.8mm hose I have - similar result.
I'll try again after warming it up, but it seems to be so wrong.

The ones I've put on from AN have been a snug fit - not overly hard.

3/16" = .1875"
4.8mm = .1889"

The 4.8mm should be a sloppy fit. So, my guess is that you have non-standard manifolds or stubs or that the stubs are covered in old rubber.

Schwany · Sep 16, 2024

Put some silicon on a Q-tip and twist it in the hose ends. Also a heat gun helps with tight hose. I use clear tire dressing to lube tight rubber hose. The tire dressing is mostly silicon. I've never had one blow off from a backfire.

I have no idea about what is right spec wise. I just do what works and carry on.

SteveBorland · Sep 17, 2024

Tried again last night, and found a length of 4.8mm fuel hose is a very snug fit after removing the woven fiber outer cover.
Still wondering why the A-N supplied hose was impossible to fit though.
Perhaps there's a difference in the size of the stubs? They were quite clean, no glue of bits of rubber stuck to them at all.
I didn't have my vernier to hand when fitting the hose and don't see any point in removing it now just to measure the diameter of the stub.

PeterJoe · Sep 17, 2024

Steve,

I've been using 7/32 inch diameter vacuum hose that's readily available at our local auto parts store. This size hose is designed to work on 1/4 inch diameter hose fittings.

Peter Firkins

Amal carb balance tube

SteveBorland

Triton Thrasher

concours

marshg246

Schwany

SteveBorland

PeterJoe

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