The 50cc race bikes of the sixties

Mike Pass

Supporter
As a antidote to the usual politics I though this might make a refreshing change and might even be interesting to the gearheads.

I was looking through some old pics of the TT back in the 60s and remembered seeing the 50cc race bikes flying round the course at amazing speeds with their tiny screaming engines. How they managed to get these things up to 120mph I do not know. At the corner where I was watching they changed down 8 gears in just a few yards and then whizzed away in a flurry or revs and gear changes like a demented wasp. They never emerged from behind the screen for fear of creating any drag. I had a good look at them in the paddock afterwards and was amazed at how flimsy they were. I was able to pick up the Honda with one arm as it was so light and even more amazed when I saw the front brakes which rubbed against the rim.

Some 30 years ago the 50cc class of the motorcycle world championship was dropped. It had survived for 22 seasons and whilst it was somewhat overshadowed by the bigger bikes it produced amazing machines and some remarkable technology.
The golden period for the 50cc bikes was in the sixties when Suzuki and Honda threw the full weight of their technology into developing these pocket rockets. The two stroke Suzukis and the four stroke Hondas battled for supremacy. By the time the governing body called an end to the category the top 50s were producing 360bhp per litre, revving to 22,000rpm and using 14 speed gearboxes.
Suzuki’s 32.5mm x 30mm twin was the most successful bike of that era and was due to be replaced by a 28 x 26.5mm triple when the madness was brought to a halt when the FIM restricted them to single cylinder motors. The final edition of the Suzuki was the RK67 which had 18 bhp at 17,300rpm and a 14 speed gearbox. The bikes weighed in at about 50Kg and ran on 2” tyres.

These tiny engines with pistons the size of eggcups and gearboxes like jewellery were not easy to ride and needed a lot of skill and technique to get the best from them. To quote Kiwi, Hugh Anderson, winner of the 50cc titles in ’65 and ’66 “You never had more than 500 revs to play with, so you were constantly monitoring the revs, using the clutch, trying to find another hundred rpm – it was minimal stuff. A little made a big difference. I enjoyed riding them because you were mentally active in a different way; you had to work very kindly and sensitively with the engine to allow it to do it’s best. I had bloody great water blisters on my elbows because they were tucked in against the cylinder heads and my calves got burned against the expansion chamber shields. I wrote it all down: change down 12 gears for this corner, 10 for that corner and so on.”

Riding the 50s was like riding a pedal bike as momentum was everything to not let the revs drop out of the incredibly narrow power band. Stuart Graham who won the 1967 TT for Suzuki –“The most important thing was carrying speed, because losing any revs would lose you a lot of time. The twin had power between 17,000 and 17,500rpm so you were playing a tune on the gearbox and keeping tucked in behind the screen to the bitter end.” Some riders seven wore boots a size too small to cut drag and all were on a permanent diet and being small was essential.
Honda only won the title once as they were not willing to get into two-stroke technology. Once Suzuki brought out the twin the Hondas struggled to even stay in it’s slipstream. The Hondas had a wider power band but needed to be kept between 19,000 and 21,000rpm. To get off the line the riders revved it to 18,000rpm and then feathered in the clutch until it got going. Honda tried everything to go faster and even used bicycle type brakes, which clamped onto the wheel rim which reduced the unsprung weight. This worked so well that they tried it on the 125cc but the rim got so hot it melted the tyres.

Honda withdrew in 1966 and Suzuki when the category was restricted to single cylinders and an amazing era was over.

Here are a few links to videos and also a few pics attached to give a flavour and everybody likes a few pics.

https://www.youtube.com/watch?v=s4PA8VFpUlc

https://www.youtube.com/watch?v=vDd0kVnnqfg

https://www.youtube.com/watch?v=B9K5YAWgiKY

https://www.youtube.com/watch?v=pYUGMVelsJw

https://www.youtube.com/watch?v=L-0AH79mY2E

Cheers
Mike
 

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Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
Fabulous read and what history!!!

I agree with Keith and have moved the thread...
 
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