50cc Racing History from 1953 through to 1983 - JEEP (AKA  J. E. Elton-Payne) 
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Brian Woolley of Shepshed, Leics. created this machine in the summer of 1966, aided by Bob Stevenson, creator of Spondon Engineering, Derby, England and it was the 50cc water-cooled Yamaha special that Trevor Burgess rode and did, in two brief months towards the end of the 1966 racing season, make a notable mark on its class. In the picture Bob is not holding the Yamaha frame. It finished second in the Irish Temple 100, setting joint record lap, raising the old record by three and a half miles and hour. It twice won at Cadwell Park and once at Darley Moor and it is the only machine to have beaten Darley specialist George Aston's Honda on its home ground. 

 

This little lady was also entered for the 1967 Isle of Man TT 50cc class. Terry Burgess was the rider and she executed herself admirably. Wearing number 26 she came home in 9th place ahead of three Honda CR110 and  within 3 minutes of the Honda in front of her.  As this was a mass start race you can see Trevor on the Yamaha taking the outside edge of the pack mid-field. 





Basically, this remarkable racing motorcycle, is a YS-1 road model sports moped engine in a home-made frame. This special was built of readily available parts with an American Gomatic gearbox which gave what is virtually a two-speed back axle to produce 8 ratios. Unfortunately, on Racer Test day at Silverstone, when the machine was put through its paces, this device gave trouble and had to be locked in the high gear, leaving the Woolley - Yamaha very severely handicapped by a shortage of close enough cogs.


 



Balancing the gearing trouble of this Yamaha against the headwind obstruction of Brian Kettle's stock Honda CR110, Racer tested on September 3rd 1966 (the Honda had a far greater frontal area), the two machines seem to have identical top speeds. Both notched 72.55 mph through the Midland MCRC electronic timer. But the important point is that Woolley's machine costs less to get to the line - and to keep running. It already has a performance to equal that of the CR110's. And development had hardly begun . . .








Trevor Burgess testing the Woolley Yamaha


Development

Ready for the track at the end of July 1966, the special was created from a 1964 YAMAHA - YS-1 engine and gearbox, a home-brewed frame, Suzuki telescopic forks, a Bianchi front end and an Itom rear wheel.

Devised by Brian Woolley and mostly built by Bob Stevenson, the two-stroke originally had an air-cooled barrel. It was temperamental and unreliable. Brazing on a sheet-steel water jacket around the barrel, with thermo-siphon circulation to a LE Velocette brass radiator, cured both vices. As of the test date, the engine was overcooled. More power was to be forthcoming with the improvement in the water circulation gaining an increase in the jacket temperature. But cylinder-distortion, prime cause of loss of stamina with highly tuned two-strokes, had been eliminated.

Another early trouble was the disintegration of the pressed-paper rotary inlet valve, which always gave up whenever asked to rev to 12,000 r.p.m. This was substituted in favour of a Tufnol disc. At first the 140deg. total-open-period of the inlet valve was extended to 205deg. but Woolley thought that the standard timing was not that far out and he later decided to come back to 195deg. The exhaust top edge was raised to give 170' timing but the three transfer ports were left alone; one port is actually split by a bridge so it could be said there were four transfers.

With a narrow power band in prospect, it was realised that the four-speed standard box would be short on ratios. A high-low Gomatic two-speeder was grafted on the rear end giving half a ratio difference.

Minor cir-clip trouble prevented it being used by us at Silverstone. Worked by a grip on the left bar, and needing no clutch or throttle action to change ratio, the American unit theoretically gives eight speeds. In reality, the rider push starts in low and bottom, changing three times on the gearbox to reach top, then shifts into high. Total: five. It is not practical to run through all eight ratios on the trot but the Gomatic's half a ratio is useful on hills to get exactly the right cog.

Triangulated, the backbone type frame was made from mild steel tubes. Suzuki forks were used because Reg Orpin was willing to swap a pair for one of Woolley's hats! The Bianchi and Itom hubs were to hand. Apart from the water-cooling, and the already-mentioned inlet timing alteration, no real tuning had been done prior to the track test day. The weight of the machine for the test was 120lbs (54.5 Kg) dry with fairing. True development was to start that winter.

Preparation

(Comments from Brian Woolley)  While reliable in a race, the machine is given considerable attention every time we get home. The barrel comes off and the rings are checked. Being very hard, they frequently break but this does not damage the piston or barrel. The exhaust system is scrupulously cleaned out -- that pays real dividends.

After three or four races the crankshaft gas seals are replaced and the Tufnol disc-valve checked for damage and wear. The ignition system gives no trouble and the contact-breaker rarely has to be touched, a novel thing amongst high revving two-strokes. For short events we use a Lodge R51 plug and for long ones the harder R53. Carburetion is remarkably consistent. We nearly always use the same main jet, a 102. Burgess likes his tyres pressured to 26-psi front and 28 rear.

 Riding

 (Comments by Bruce Main-Smith).  Added to Owen Greenwood's Mini and Ray Flacks kneeler-Norton, this Yamaha forms the third of a memorial trio in the Racer Test series. It was different and it was fun. There's something appealing about a racing engine which doesn't have or need a rev counter. "Rev it until it goes flat". Those were Woolley's instructions. The Picture is of me (BMS) 'bump-starting' the little 50cc YAMAHA


I found that it sang on and on until the shriek of the exhaust seemed to stop rising. Then I snicked another one in. It was that simple. Moreover the engine was very clean down at the bottom-end, whereas some highly tuned two-stroke engines are next door to impossible. The lack of the extra gears was an undoubted handicap. I held third past the Silverstone pits and after a few laps managed to keep the Yamaha as flat as a kipper round Copse. Top gear went home near the crest before Maggot's left-hander.

Being a 50 and not a 500 it was consequently on full rattle for quite a time and the long bomb down the timing straight together with the very late shut off points were more spells of continuous full throttle.. I kept at it yet the engine never tired, Water-cooling was playing its part.

The little single was vibration-less at any r.p.m. -- whatever they were -- and ever willing. Unlike Kettle's Honda this baby racer was free from drifting, common with to many 50's on corners. It was like riding a bigger bike. Cornering speeds were much higher than I realised, or learned in a dozen or so laps to use. Ground clearance was abundant and adhesion at high angles of bank very good indeed.

Mounting the footrests on the un-sprung part of the rear end gave a curious sensation of the feet rising and falling as the rest of me stayed still. It didn't spoil my gear changing and I can't help wondering if the increase in un-sprung weight didn't improve handling on bumps for a machine of such extreme lightness. It certainly did not spoil anything because the Yamaha steered impeccably and held the road like glue.

The brakes were entirely adequate and the gear-change light and neat. Push starting could simply be a sit-on-and -paddle job. Just as easy to ride this little special was rev-proof, un-burstable and un-tirable, give it the 12 cogs of a racing Kreidler and it would go places. As it stands it is a pretty cheap, and yet competitive 50.

Test Data:

Track: Silverstone Club circuit 1.608 miles (2.57km). Timing straight 0.6 miles (1 km) with 30-mph approach corner (Becketts) and 50-mph exit corner (Woodcote)
Conditions: Calm winter day. No wind. Temperature from 4°C falling to -1°C. Dry.
Track speed equivalent to peak power r.p.m. of 12000: 1st gear=30mph, 2nd gear=50mph, 3rd gear=70mph, 4th gear=95mph.
Best speed through trap: Burgess, 72.58. Main-Smith, 69.23.
Best flying lap: Burgess, 60.1 mph. Main-Smith, 52.00. (Bruce is much taller and heavier than Trevor)


YAMAHA 50 CAN HOLD THE HONDA (A response from Brian Woolley to comments made about the YAMAHA 50.)

I THINK Bruce Main-Smith  will agree that I gave him no “old hat” regarding the 50 Yamaha tested -by “Motor  Cycling”, and that despite Bob Latham’s strictures (January 21 issue), the bike will stand or fall on its own merits.  

I was at fault in not checking more closely on the Temple 100 lap speeds, but I was told that Trevor Burgess, on the Yamaha, and Bob Latham shared the fastest lap. 

So far from the nonchalant “I passed and left it behind” with which Bob dismisses the  Yamaha's Enduro performance, my recollection is that, after trying to stay with the Yamaha for two laps, his Honda rapidly fell back! 

Bob himself wrote to me sh0rtley after the Enduro, saying “I was amazed at the speed of the thing. It must  push out a phenomenal bhp. From a point somewhere on the Norwich straight, its top speed was undoubtedly higher than the Honda's.” 

I notice that in this letter he does not complain of the Yamaha’s handling and, having watched Trevor at several  circuits, I do not know what he means. 

I lent the Yamaha for a racer test to encourage the 50 class, and to show that a truly home-built special can live with the Hondas.---BRIAN  WOOLLEY Loughborough.  

 

The Write-up from the Bonham's Catalogue

The 1966 Woolley Yamaha 50cc Racing Motorcycle:

Motorcycle engineer Brian Woolley was one of Britain's foremost two-stroke engine specialists and is perhaps best remembered for helping to develop the Greeves Silverstone production racer. The unique machine offered here was created by Brian in collaboration with Bob Stevenson and first raced in 1966 by Trevor Burgess. (Please note that the pictures here are of the bike on show in the Lexmond museum in the Netherlands).

 

It is powered by a 1964 Yamaha YS-1 roadster engine modified by the addition of a water-cooling jacket in the interests of reliability. Tuning work consisted of the usual 'port job', fitting an 18mm Dell'Orto carburettor and replacing the rotary inlet valve's compressed paper disc with a Tufnol part giving longer opening. 


Small capacity engines with relatively narrow power bands are best served by multi-speed gearboxes (Suzuki's 50cc RK67 twin used 14 speeds!) and Woolley ingeniously doubled up the Yamaha's four ratios by using an auxiliary transmission in the form of an American-built 'Gomatic' high/low unit, carried on the swinging arm's left leg.


Motor Cycling explained the change procedure when its tester Bruce Main-Smith rode the Woolley Yamaha at the end of the 1966 season:  'In reality, the rider starts in low and bottom, changes three times on the gearbox to reach top, then shifts into high. Total five. It is not "practical" to run through all eight ratios on the trot but the Gomatic's half a ratio is useful on hills to get exactly the right cog.' The modified YS-1 engine was installed in a purpose-built spine-type frame equipped with Suzuki front fork, Bianchi front brake and Itom rear hub. 


BMS found that the bike 'steered impeccably and held the road like glue. The brakes were entirely adequate and the gear change light and neat. Completed in the summer of 1966, the Woolley Yamaha with Trevor Burgess aboard had won twice at Cadwell Park, once at Darley Moor and finished second i n the Temple 100 in Ireland by the season's end. Motor Cycling estimated the Yamaha's top speed to be the same as that of Honda's CR110 over-the-counter 50cc racer – not bad for a home-built 'special'.

Kept on museum display for the last 15 years, this unique racing '50' is in running condition but will require re-commissioning before returning to the racetrack. The machine is offered with a copy of Motor Cycling's article and a quantity of spares. 

Sold for £7,245 inc. premium

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