These hand-crafted carburetors are very impressive. But, given that they have bodies that are of different size than any original TT along with MkII Concentric (or other) internals, are they threading their way between paragraphs in a rule book, or are such custom components allowed without question? Does their existence rely on the fact Amal produced at least a few in this bore size, or in principle could someone produce an even larger casting to result in a, say, 1-3/4" TT and still be within the rules that these carburetors are constrained by?
It depends on the organization, but the clear line in road racing is that the item copied had to be original equipment, particularly in the case of carbs, with the size. I could not use an equivalent size GP even if there were one. But, the rules differ within organizations themselves. In AHRMA class C you are restricted to 4 speed transmissions even if the original was a 5 speed. In Premier 500 you can run a 5 speed. The carb above is well within most road racing rules. They are surprisingly concerned with appearance and you can run brand new Gold Stars and Manx motorcycles with no issues.
In LSR, land speed racing, they are much more concerned with "period vintage." A new part (later than 1956) must be pre-approved and identical in design, no big bearing journals, no increased wall thickness, etc. For example, in SCTA you have to use a "real" magneto, nothing "reactive" or electronic. They seem to interpret this rule as meaning no advance or retard, but fixed ignition only. So, in AMA at BUB you can run a new BT-H electronic ignition, but it is not allowed at SCTA. In fact, the stock ATD or a manual lever would not be allowed. (In LSR there are engine classes and chassis classes so, I am just focusing on engines.) In contrast, you can run any carb or any transmission (with any number of speeds) at both venues in the Vintage class. Thus, the spec you build for is the one where you will run the most. It makes it difficult for the over-seas LSR guys who run at home and then travel to Bonneville. They often want to go to both BUB and SCTA to get as many records as possible. But which do you build for? Home? AMA (BUB)? SCTA? You choose the design you have done the most development with and hope you do not get protested at the others.
David
