WORDS BY Oli Hulme
ARIEL’S 650CC HUNTMASTER. It’s just a BSA Flash A10 in sensible shoes, right?
That’s a common opinion… and it could not be more wrong. Certainly, the engine can use some of the parts from the A10 power plant under its Ariel cases, but the rest of the Huntmaster is all Ariel.
n fact, BSA saw so much that was good about the Huntmaster that later on it nicked the brakes for its own models.
The 650 appeared in 1954 when Ariel had to come up with a new big twin to sit between the 500cc Fieldmaster and the behemoth that was the 1000cc Square Four.
By this time Ariel was in the hands of BSA and the Small Heath management could not countenance the spending of money for a brand new 650cc twin engine just for Ariel.
The existing engine on the 500cc Fieldmaster twin could not be taken out to a higher capacity.
The Ariel 650 twin was the third British motorcycle to be made postwar in this capacity, following a strategy started by BSA and Triumph.
While other manufacturers were happy to simply slap different branding on near identical motorcycles, BSA practice was to let its brands compete with each other properly.
Which was why BSA and Triumph produced such wildly different motorcycles despite having the same parents, and also why Ariel was doing things differently to both of its siblings.
For the new 650, BSA built Ariel a version of its A10 engine built at Small Heath then shipped it to the Ariel factory at Selly Oak.
The engine shared its internals and cast iron cylinder head with the A10, but outside it had a properly cast Ariel badged timing cover over an Ariel specific timing chest, a more compact valve cover that made it easier to adjust the valve clearances than on the A10, and a different timing cover and clutch.
The clutch was a dry Burman unit that was lighter than the A10 version, sitting under a smart chromed cover, and the primary drive arrangement required different mounting bosses to be built into the crankcases.
Read more and view more images in the June 2019 issue of CBG – on sale now!Enjoy more Classic Bike Guide reading in the monthly magazine. Click here to subscribe.