Mr Hele, a question

Dear CR

Great to see those lovely pictures and words about the ‘Rob North’ BSA Rocket 3 in the last issue. It’s good to see an original bike with genuine 19in wheels, forks and period Dunlop tyres.

The part that interests me is that it was always said that the T150 was made by adding a cylinder onto the company’s ‘current’ 500 twin when the two possibilities were the pre-unit T100 and the unit T100.

The first had 63 x 80 bore and stroke while the latter (which Triumph had enjoyed racing success with) was 69 x 65.5. To me, it seems that the T150 shared its engine dimensions with the humble BSA C15 which was the only engine in the range with 67 x 70 dimensions.

I wonder why Mr Hele didn’t go with the 69 x 65.5 measurements?

Graham Curtis, Derby

Read more letters in the May/June issue of Classic Racer – on sale now

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