518cc, not sure on the other details, and I am not sure it is fair to guess or put a tuners head details on a forum.
Hi Ace,
It is one of mine and pencilled in for 'Asbo' No 19. Presently, we have a rebuilt bottom end with my trademark lightened crank, which is fitted with a forged steel conrod and roller big end. The cams I asked about at the beginning of this thread are fitted at present.
The cylinder head has been ported [by me] to a nominal 34mm inlet, flaring out at the manifold flange to 36mm, to give a margin should a carb of that size be required. The head was ported before I had the rest of the engine and taken off the shelf to contribute to this project. This engine is one for which I have slowly been working on isolated components, resulting in a more or less complete engine to assemble, short of a decent piston and alloy barrel at present. It was to be built as a complete engine before being made available, but I was asked if I had anything.
I intend to offer the so-called 9:1 American made piston from Hitchcocks, in a +0.060" oversize if available, although I rate them at 7.75:1 and will shorten the barrel by 2mm, to get closer to a true [by my calculations] 9:1 compression ratio.
It is not intended to build a revvy engine, similar units I have built in the past give around 30bhp @ rear wheel at around 5600 rpm or thereabouts, with good power from low engine speeds and a sharp torque rise.
I think we will be using standard valves, with competition springs, although any number of changes could be made to many of the specifications at this point, should they be requested. This engine build is aimed at lively acceleration from relatively low engine speeds, thanks to the lightened crank and getting quickly into its' torque zone, with the capability to rev to around 6000 rpm at times.
I have suggested an 18t gearbox sprocket, to aid a higher cruising speed, while not detracting too much from acceleration by going any larger, but the final decision will not be mine.
I also suggested a 32 - 34mm carb for this application.
B.W.