Bored out B31, which thuds along very nicely at the price of loads of primary vibes, effectively limiting speed to 50/60mph unless the crank’s been balanced and the engine put together with unusual skill. Go for the later swinging arm version, preferably with TLS front drum conversion and upgraded suspension. Some nice cosmetic renovations but with dodgy mechanicals, in dealers, so take care! Gold Star version’s too expensive.
1945-60 499cc (85x88mm) OHV single 24hp, 85mph, 70mpg, 345lbs