Similar motor to the old Honda CB350/500 fours which begin to suffer after 25000 miles – mostly from the top end, clutch, gearbox and alternator. The 504 was the most successful of the series in the UK, the smaller fours rare and the 654 somewhat fragile. Honda motors will fit into the useful chassis. 254 amazingly lightweight and small for a four cylinder bike. All are becoming rare, these days, and not really worth going wild over.