The Scene
THE SCENE
IVAN J. WAGAR
How complex will Grand Prix machinery become? These first “naked” photos of the Yamaha four reveal a plumber’s nightmare, but it seems that to obtain 150 mph (requiring about 60 bhp) from a 250cc two-stroke, this is the way one must go about it. The photos taken at the Ulster GP show more clearly how Yamaha have engineered two 125cc twins into a single package, with the two engines set at approximately 70 degrees to each other.
It is safe to assume the upper engine runs “backwards” to accommodate the rear-facing exhaust port. This would normally be dangerous practice on an air-cooled engine, because of probable piston seizure, due to very high temperatures in the exhaust port region at the back of the cylinder. However, Yamaha has eliminated this problem by using a gearbox-driven water pump, which ensures positive coolant circulation at all times. The temperature gauge is mounted close to the upper fork crown, while the electric rev counter is forward on the fairing mount.
The engine peaks at 14,000 rpm and drives through an eightspeed gearbox. Separate electronic ignition systems are used for “each” engine. The four is now fitted with new, massive front brake.
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Guess which photo shows the sparkplug access flaps open on the new Yamaha 125 four. The machine was flown from Japan for the Ulster Grand Prix, but after preliminary practice laps by Phil
Read and Tommy Robb (replacing Bill Ivy), the machine was returned to the paddock and remained idle during the race proper. Read and Robb used the twins in the race and finished third and fourth.
Amid much conjecture, it was generally concluded that the new four remained inactive because learning to ride a totally new machine in the practice time allowed before an important GP, particularly on wet roads, would not be worth the risk. This was further supported by the knowledge that Yamaha can still beat Honda for the 125 manufacturer’s championship.
The truth of the matter is that the bike is purely an experimental piece and will not be raced this year. Yamaha explained that its presence in Europe is to allow works riders to test it under near-race conditions without actually competing on it.
The four’s existence was a surprise to everyone, as it has been felt lately that Yamaha would scale up the 125 twin to get a better handling 250. There are no horsepower or rpm figures at present; however, an 11-speed transmission indicates an exceptionally narrow power band.
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AGOSTINI is certainly creating a stir with the new MV 420cc “three” and has even been giving Hailwood an eyeful lately.
The engine is a scaled up version of the 350 “three” introduced last year, using four valves per cylinder. Horsepower is reckoned to be 76 at 12.000 rpm and a top speed of 158 mph with Spa gearing.
As frames become lower, camboxes and sumps larger, the space problem becomes more critical and MV is faced with the same problem facing Honda when it comes time to remove the engine.
Like Honda, they have made part of the frame removable. The left front down tube slides into a mating extension from the main cradle, where it is bolted in place. It is then bolted to the rear fixing point just behind the engine/transmission unit.
LIKE some of our readers, we are never totally pleased with CYCLE WORLD. We feel strongly about our obligation to the sport and to those who participate in it and, as a consequence, are constantly exploring new ways of improving our reporting to provide our readers with a magazine that is interesting and valuable.
Beginning with this issue we are adding two new variables to the road tests and impressions of scramblers and lightweights. These new values, elapsed time and terminal speed for standing-start 1/8 mile, are much more meaningful for motorcycles in these categories than 1/4-mile times. (In the case of the larger scramblers, we will test for 1/4-mile times and speed (Continued on page 30) also.) Our reason for adding the 1/8-mile testing is obvious; a scrambles machine will come close to its maximum speed in this distance if it’s set up properly. We find this also to be true of the small capacity lightweights. We feel that the new values are well worth the effort and hope they will truly make the tests more meaningful.
THEY said it couldn’t be done (those Triumph chaps), and with good reason. The problem: add an electric starter to actress Ann-Margaret’s 500cc Triumph twin. The task fell to talented - and game — motorcycle builder A. J. Lewis. Beginning with a starter from a 125cc Yamaha, A. J. machined, drilled, cut, welded, wired, and polished his way to as neat and ingenious an installation as could be imagined. The secret of the system lies in the clever compression release arrangement. Release valves have been installed in the spark plug holes and new plug holes were drilled and tapped vertically into the tops of the cylinders. The system works quite smartly simply by first venting the cylinders, winding up the starter and then dumping the compression release. We have doubts about the appearance of a 500cc Ann-Margaret Electric Trophy Road Sports in Triumph’s line next year; however, this nice little modification set the young lady back $600! that if a rider is not under contract to a petroleum company (Fritz is not), he must use the fuel supplied at the race. During practice Fritz attempted to obtain course fuel but was refused any. A resourceful and reasonable man by nature, Fritz then went to a local garage and fueled up with Esso “Golden,” a pump gas. At the post-practice weigh-in, Fritz stated on his declaration card that he was using Esso “Golden.” The officials saw the entry, checked it and said nothing. Several hours after the race - which exacted a very high toll of the components of Fritz’ BMW outfit — he was told his efforts were for nothing. The A-CU later admitted that they had erred by not pointing out their ruling to Fritz, but would not back down. And how does Fritz view this? He told a reporter from the British weekly “Motor Cycling” that if he is not declared the winner, he will (Continued on page 32) never race again, and will finish with the sport completely. This fine Swiss gentleman-sportsman has been racing for 16 years and throughout that time has never failed to observe the rules. And now, after pulling off one of the most exciting wins of his career, he is robbed of the rewards that attend it. The A-CU has found a comfortable hiding place by stating that because the discrepancy had been called to their attention by a third party, they had no choice but to disqualify Scheidegger for breaking the rules!
IF you think we are unhappy with our home-grown competition rule-makers, you should hear what is being said around the CYCLE WORLD offices about the A-CU’s cute stunt with World Sidecar Champion Fritz Scheidegger. While celebrating his first-ever Isle of Man TT win, Fritz was informed by the officials that he had been disqualified for using a brand of gasoline that, technically, he was not allowed to use. The A-CU ruling states
THIS Honda mechanic is really not having trouble understanding the number three in front of him. The number is Hailwood’s grid position and the mechanic is using the Japanese method of “eyeballing” the rear wheel, while another mechanic adjusts the rear chain.
AFTER the Russian Motocross GP, a real party got underway in the Leningrad Hotel, where the riders were staying. Race organizers were handing out Vodka by the jug full, and in the end, some of the riders, six floors up in their rooms, decided to clear out part of the furniture — via the window. The hotel management didn’t mind this, however, as the riders discovered the next morning, when they were refused the return of their passports until $300 had been coughed up to pay for the damage. Already CZ have started to make plans for next year, and during the winter months, experiments will be carried out with a 400cc machine for the large class. It has been found this year that while the factory single-exhaust models give out some 3 bhp more than the two-pipe type (available in the U.S.), the extra power is at the top of the power range, and with riders having to give the machine full throttle, the handling of these machines has not been as good as the production machines. The answer seems to be that if the factory engineers increase the model’s stroke to bring the engine size up to 400cc, the porting can be altered to bring in the power punch lower down. It is hoped that this will help the riders to get quicker starts, better power out of corners and better handling. CZ hope that Friedrichs and Tibblin can look after the 500cc class by themselves next year, and have asked Dave Bickers if he will return to the 250cc class to help Joel Robert and Russian Victor Abrekov fight off the Husqvarna challenge. ■
