250 power

[neandethal]

According to the service manual the sx/ss/sst 250 lost power as it aged, pre-75 sx's made 21.4bhp, later bikes 19.2bhp and allegedly all ss/sst only 19.0bhp.
Does anyone know why, exhaust profile perhaps, would rather have 21.4 than 19 I have to say!! Just interested.

 

[Paul P.]

Coming into the seventies HD advertising was still prone to the sort of exaggeration that characterised much of American advertising, for example factory ads for the road models used to heavily imply that they had some relation to the RR250 that was, in the mid seventies, winning world championships. We did see later on the wording in at least GB adverts being altered to correct this. So I wonder if the dropping figure was as simple as telling the truth?! Back in the day the 125/175/250 were maximum speeded at 70/75/80mph with maybe a couple more mph from particularly healthy machines.

(for readers who don't know the RR250, the only thing it had in common with the catalogue models was...250cc!)