Stainless Steel "Big Bore" 32mm Intake manifolds for Vincent Twins, and Singles.
For mounting Amal Mk.1 Concentrics available in 28mm, 30mm, and 32mm bore sizes. These are excellant carbs used in the British market in the '60's, and '70's. This is the carb that Mikuni copied.
$220.00 (Includes: Manifolds, Bolts, Nuts, Washers, Instructions, Drawings, and Partslist.)
Manifolds shown with a K&N (RC-1290), and New Carbs (Amal 932's). Manifolds come with hardware, gaskets, instructions, tuning, and jetting specs, drawings for cable lengths, and partslist.
K&N RC-1280 Air Filters that are larger for more breathing.
Manifolds, and Amals with a K&N (RC-1290) Filter.
Manifolds during construction.
Here is my 1951 Rapide showing the new Amal Mk.1 Concentric with K&N's installed. This combo allows me to get the full benefit from my Mk.2 cams, and my 1,164cc "Big Bore" motor with 10:1 compression. Yes, it pulls like a freight train!
These manifolds are hand made from Stainless Steel, and they closely resemble the original manifolds in shape, and placement of the original Rapide, and Shadow cast manifolds. Due to the original casting thickness, there is a safe limit for boring the original manifolds. The closeness of the mounting nuts makes it hard to make a runner of any respectable size due to the thick wall thickness of the aluminum manifolds. I use thin wall Stainless Steel tubing welded closely to the mounting nuts, and there is a full 32mm inside bore width. This increases the flow area by 52% over a stock manifold. They are finished in a fine satin "Glass Bead" finish, and can be polished, or finished with "Scotch-Bright" pads.
Why do you need Amal Mk.1 Concentric Carbs?
As mentioned before, the inside bore size of the original manifolds is very small at 26mm for Rapides, and at 28mm for the Shadows. There is no point in trying to gain any performance by modifying a stock manifold for a newer, larger carb. For this, larger inside bore manifolds are needed. These 32mm manifolds are a practical size, because the port size of the heads are very close to 32mm. The little bit of extra port material in the head allows you to "port-match" my manifolds to your heads easily with a dremmel tool with a sanding barrel attached. The Amal Mk.1 Concentrics are very compact, and the placement of the carb is identical to that of the originals. Larger carbs than these must be extended farther outwards, which fouls the riders legs, and just doesn't look right. There is no advantage to using a larger carb than the Concentric 932, since you are limited to the port size of 32mm. Now, a better K&N air cleaner can be used, and all of the poor qualities of the original carbs can be eliminated. The Concentrics allow you to use the bike without fear of leaking (and fear of fire!), with easier starting, better idleing, and a vast increase in power. Jetting is much easier, and I am providing a guideline for correct jetting included with the manifolds. You should save your original carbs with the bike, but now you can ride your bike with confidence, and actually get some use from your investment! My drawings, and instructions make it easy for you to make-up (or to have made) new throttle, and choke cables. The original petcocks, and fuel lines can be used. Only the fuel line ends at the carbs are changed. I have used this setup for years with great satisfaction, and I have been able to actually ride, and enjoy my Vincent.
James R. Mosher