HS2 Carb - Idling Too Fast

[Iris.Caretaker]

Hello:

(First time poster - looks like a great forum! I just solved a horn push issue with your help. Many thanks!!)

I have just installed a Moss-rebuilt single HS2 carb in my '65 Austin Mini Deluxe (848cc). I have it running with the ignition timing set and what I think is a proper fuel/air mix, but I can't seem to get it to idle at less than about 1,500 rpm. I have installed what seems to be very powerful throttle return spring but that still doesn't bring it down to about 1,000 which is what I think (but do not know) it should be.

The carb body indicates the following stamped spec: AUC82.

I am wondering about the needle, but I would have thought that Moss got that right. And I'd rather not rip it apart to change the needle if that's unlikely to be the cause.

Any insights would be gratefully received!

[Terence]

Have you tried putting a cap on the vacuum advance nipple seen in pic two?

[timmy201]

I’d pull the needle out and check what it is. You also need to make sure the mixture is set correctly, the spring and damper oil are right

AUC82 is the casting number for the carb body and doesn’t relate to any particular spec

[Oneball]

What Terence said

[olddave]

And a tiny bit of free play in the throttle cable.

[Iris.Caretaker]

Thanks to all! I will be able to get back to tinkering on the weekend. I will try your suggestions and update you all about the outcome.

[LarryLebel]

Maybe Moss installed the throttle plate backwards.

[Terence]

Maybe Moss installed the throttle plate backwards.

Or not centred. I bought a set of JanSpeed carbs a few years back that I couldn’t get a consistent idle with, turned out that the throttle plates on both were not centred. There was also a burr where the vacuum nipple port was drilled that was causing the throttle plate to hang up.

[Herbert]

idle is controlled by the amount of air going into the manifold. You have , without doubt an air leak, Good luck!

[mk1]

As Terence has already said, the spigot for the vac advance has nothing connected to it. Blank this off & the air leak you UNDOUBTEDLY Have should go away.

Do this before anything else.

[Iris.Caretaker]

Hello, All:

Well, it took me longer than I expected to have time to try out your various suggestions on idle issue, but the winner was Terence, who was the first to suggest blocking off the breather hole.

It works like a charm, now. I may need to get a neck brace to handle the 34 bhp out of the blocks, though!

Many thanks again!

[Terence]

Hello, All:

Well, it took me longer than I expected to have time to try out your various suggestions on idle issue, but the winner was Terence, who was the first to suggest blocking off the breather hole.

It works like a charm, now. I may need to get a neck brace to handle the 34 bhp out of the blocks, though!

Many thanks again!

Glad to hear that you got it sorted! Now go and enjoy the fuel economy