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The BSA 500MX 1971-1973

By MATT CUDDY

The BSA 500MX 1971-1973

BY MATT CUDDY

After suffering through the 441 disaster, in 1971 BSA came out with a new motorcycle that would hopefully repent for sins made by the 441, and save BSA from a fate worse
than death.

This new bike was called the B-50 500 MX, and was Beezer’s last gasp at producing a motocross motorcycle of any significance. In fact, it was the last MX bike BSA would
produce, as BSA folded in 1973, and was absorbed into the Norton-Villers-Triumph fiasco of 1974.
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1973 BSA B50 500MX

The B-50 was one serious looking machine, with a polished alloy tank; alloy motor, conicle hubs and a big stonking 500cc mill to complete the package. Betor or Metal Profile forks graced the front, while the rear end was propped up with miserable Girlings that lasted about an hour under the rigors of MX. The 500MX was distilled down to the basics, with no unused brackets or other stuff from the trail version being incorporated in the B-50's design. A clean machine.

The engine was derived from the B-25 250cc machine, with upgraded larger internal stuff to support the five hundred’s increase in power. A needle roller big end bearing,
and other quality items made their way into the motor of the 500MX, and it seemed BSA finally had a winner.

1971 B50 BSA Note sagging milk crate.

But alas, the B-50 500 MX suffered from the same problems as the old B-40 (441) did. While BSA tried to lighten the 500MX by using as much alloy as possible, and the frames top tube as an oil tank, the bike still weighed in at a portly 310 lbs full of fluids, and put out a measley 34 BHP at 5000 rpm. Not what you needed to beat the competitive 2 strokes of the time, that weighed a little over two hundred pounds, and put out just as much power, if not more.

Not to say the 500MX was uncompetitive, and put in the hands of an excellent rider, the bike could keep up and sometimes beat the two stroke machines of the time. But that was a rare feat indeed, when racing against works Suzukis and Huskys of the time.

Feets Minert campaigned a 500MX in the USGP series of 1971, and usually placed in the top five positions. John Banks rode a much modified B-50 re-engineered by CCM, called the “Clewes Stroka” that sported titanium bits that got the weight down, but Banks was plagued with exploding motors and frames that would snap in half, ending his bid for a good finish most of the time.

The 1973-74 versions of the B-50 were “last gasp” bikes that, while neat to look at, were uncompetitive to the point of silliness. Whoever designed the “dual collector” exhaust
system on the 1974 500 was probably hauled away in a straight jacket, never to be seen again. In 1974, the B-50 was re-badged as a Triumph, and looked even goofier than the 1973 model, with a purple paint scheme and those dual trombone exhaust pipes.
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Wow, play me a tune...1974 Triumph B50

The B-50 lived on for a few more years in the hands of specialty shops in England like Clewes, CCM and Rickman, but by 1978 the big thumpers were relegated to play bike
status, and became a “cult bike” that some still worship and covet to the point of insanity.

1974 CCM 610cc "Stroka"