Hello all,
I've just joined the forum and I am looking to compete in the M-VG-350 or MPS-VG-350 bike classes with a trusty (sorry that should have read rusty) BSA 350cc Rigid Framed B31 ... (if I can find a high compression piston!).
I am based in Buckingham, England (UK) and have raced 'bikes, cars and gearbox karts in my youth (first 50 years of my life) and now I am intrigued about extracting power for straight line speed ... so, I have a dream to take to the salt (and the sand over here in Wales at Pendine Sands) in something that I can assemble from vintage BSA stuff lying around in the garage from previous projects.
I have a question about the 2019 rule book if I may ... it says I am allowed up to +0.50" overbore in the VG class - but then states ?... only if the OEM bore diameter is within 0.050inch (1.27mm) of maximum class displacement and will be discounted when the bore size is measured.?
Standard bore and stroke for this bike is 71mm x 88mm respectively with a standard capacity of 348cc. My schoolboy hard sums tells me that a 0.020" overbore will put me at 353cc - as this exceeds the 350cc limit, I am guessing it means that I will have to compete in the 500cc class?
I can get high comp ZB32 Gold Star pistons at +.020" and +0.040" but not at STD bore ... this has resulted in much gnashing of teeth etc.
So, if anyone can help in interpreting the rules with regard to overbore or in procuring a STD bore High Compression piston ... then I'll be mighty happy!
Thanks all, Rob