ET: Engine (Twin) Carburettors 1952 Black Shadow

[Geoff12]

I am thinking of changing the carbs to Amal 389‘s, does anyone have experience of fitting these and performance - or advice of whether to change from the original 289’s?
plus can anyone tell where I can purchase the flange adaptors to fit the 389’s?
thanks

 

[b'knighted]

Hi Geoff,

Series Ds were fitted with monoblocks from new so there should be a lot of info out there.

It is generally reckoned that if you ask five Vincent owners the same question you’ll get at least seven opinions.
Monoblocks seem to have a poor reputation and I would fit Mk1 Concentrics in preference. Many people seem to hate Mk1s but I dislike later carbs without a tickler.

New Original pattern carbs are available and should cure any problem you are having.

 

[Bill Thomas]

There is a pair of adapters on ebay ?,
I would think Surrey cycles , Would stock them ?.
For settings Don't forget the main jets for monobloc's use 280 to 300 ,
Where as Concentric's 220 ish !.
Good Luck, Bill.

 

[b'knighted]

The adapters are listed by VOCspares in the cylinder head section.

 

[kinsellm]

There is a pair of adapters on ebay ?,
I would think Surrey cycles , Would stock them ?.
For settings Don't forget the main jets for monobloc's use 280 to 300 ,
Where as Concentric's 220 ish !.
Good Luck, Bill.

Do you know why then main jet settings are so different? Seems odd when the bore of the carburetor is he same

 

[Bill Thomas]

Sorry no, I was playing with a Comet and Monobloc,
And I think I FORGOT !! about the main jet, But it was too heavy and I gave up after a bit,
It was rubber mounted and it fell off !!, I do play too much sometimes.
I have used so many different carb's on my bikes , Strange racing ones and all sorts,
And they all went well,
But that monobloc upset me
I think it's all about air flow, But The "D" Latest Vincents As Ian said used them OK,
And got good MPG out of them, So if that's what you want, The settings are in the Book.
Good Luck, Bill.

 

[andy tarnik]

I am thinking of changing the carbs to Amal 389‘s, does anyone have experience of fitting these and performance - or advice of whether to change from the original 289’s?
plus can anyone tell where I can purchase the flange adaptors to fit the 389’s?
thanks

Make the change . All around performance is worth the expense . Use only the 389 Premier carb. Add the roll off stand and enjoy easy one kick starts .

 

[Geoff12]

Make the change . All around performance is worth the expense . Use only the 389 Premier carb. Add the roll off stand and enjoy easy one kick starts .

Thanks for feedback, what is the difference between a standard &premier 389 carb?

 

[Mike 40M]

Why Concentrics have smaller jets than Monoblocs.
A carburettor sucks fuel from the float chamber up in the venturi.
Fuel level in a Concentric is higher, so much easier to suck up the fuel.

 

[vibrac]

There are a range of adapters available from the Spares Company covering most combinations of size and carburetor (even Mikunis!)