I keep reading this rule over and over and I can't figure out it's meaning for Vintage motorcycle engines regarding allowed overbore and effect on displacement class: example: "In all cases, the resulting displacement shall be exceeded to qualify for the next higher class."
seems contradictory to me.
7.D CLASSIFICATION of DISPLACEMENTS, FRAMES, ENGINES, and ENGINE TYPES:
7.D.3 Engine Displacement Classes:
Displacement shall be greater than the maximum allowable for the next lower class. To permit minor reconditioning of worn cylinder blocks in classes other than Production, it is permitted to increase cylinder bore diameter .020 in. (.508 mm) beyond that which provides maximum displacement for the class only if the OEM bore diameter is within .020 in. (.508 mm) of the maximum class displacement. In all cases, the resulting displacement shall be exceeded to qualify for the next higher class. The .020 in. (.508 mm) will be discounted for record certification and will be noted on the certification card and in the logbook.
Vintage engines are allowed +.050 in. overbore, see section 7.J.10.
My example: I have a real, correct 1954 BSA 500cc Gold Star I would like to race in the vintage pushrod class. Stock Bore/stroke is 85mm x 88mm for 499cc. The rule above says I can overbore .050" (1.27mm). the resulting displacement will be 86.27mm x 88mm for 514ccc. Does the rule above mean that the .050 (1.27mm) overbore will be discounted/forgiven for record setting purposes, and bike would be treated as 499cc bike, to run in the (500cc class)?
Another question about the same bike. Again, it is a correct 1954 500cc Gold Star. But the bike was also available with a 350cc engine. Same frame, but had a different number designation. Same engine, just the bore (barrel) was different. Same outside appearance. Could I put a 350cc barrel on it and run it in the 350cc class?
Couldn't find this exact question in the search. Maybe the answer is obvious to everyone else.
Thanks, Jeff