HOME and how to join Forum Open Area General Scott topics Updates to Moss Engineering site Re: Twin carb manifolds

Richard Moss

Well, you can tune for different reasons but if it is to get more power, then it usually involves getting the engine to inhale and then burn efficiently more combustable gas. If the flow through the carburettor is too resticted it can obviously limit the intake. We do a lot of work on our engines to increase the engines ability to breathe but I have been told that a standard Scott also responds well to an increase in carburettor size. This is something we have never tried as none of our bikes have ever been standard!
The Engine you see in the picture is actually a short stroke engine that we rebuilt for a customer with ‘Moss’ Cranks, and all the gas flowing modifications we offer. Basically apart from being a short stroke it is the same specification as yours Carl. The owner wanted to Sprint his machine, or at least have the option to use it for competition, and so maximum performance was an issue.
The problems with getting big Carbs for Scotts has always been that there is little available without using an adapter to a stub or Triumph type flange mount, yet with many models (single downtube) there is little or no room to get anything much bigger in anyway..(see pic of my racer here).
The whole reason for the strange scott flange is in the fact that the earlier models had a 90° bend in the carb manifold (see here) just to fit in front of the frame tube. They solved the fixing problem by using a three bolt fixing with the right hand one lower to be accessible.
Later models without this manifold merely inherited a design that no longer retained its reason of existance.
I think this is quite common!
The Beauty of this manifold is that it fits single downtube and duplex frames and also enables the use of relatively inexpensive and attainable small bore carbs on flange fits.
The only reason my father went to such extremes to produce his own Large version of a single TT carb (click here) was because of vintage racing regulations at the time.
We need to experiment with carbs and jets to give people a good starting point for use, but in all, We think this is a very elegant solution to a very old problem.
And it looks great!