Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/126655
Q(') -.. 00 (j) Q (') .... ::s bO ::s (I) < thoM'" va."......-cyIInder motor wes a roiling testbed. velocity sucks ruicI.. nMrIy 140 horaepower. The four- A two-piece drive shaft routes power from the five-speed gearbox t o " rear wheel. The brake is a cast iron disc. A full fairing and dual headlights were ~ounted for the 1978 801 d'Or 24-hour endurance race, where the bike made its only appearance. Tucking in behind the wind screen with clip-ons in hand gave a top sp"c! of over 175 mph on the long straight at France's Paul Ricard circuit. Under .(Continued from page 19) 22 fit a reduction gear to the clutch which tbus rotates in an opposite direction to the crankshaft. In addition, we fitted a contrarotating gear on the generator shaft, and tbe effect was that all the forces canceled each other OUl. Tbat was one problem solved." Laverda continued, "But the other one was much more diHicult, because we had the same torque reaction problem at the rear wheel, which would rise and fall sharply on tbe suspension under acceleration and deceleration. Again this wasn't a problem on less powerful machines with shaft drive - I've been a BMW owner for years and you just learn to live with it. But witb 140 horsepower, such a machine becomes unrideable, and that's wbat the V-6 was at first, I'm afraid." After some bead·scratching, the de· sign team came up with the answer, which was to revert to a conventional twin·shock rear end (using Marzocchi units with remote gas chambers) and to redesign the transmission casing and crankcase castings so that the now much longer swingarm could pivot about the calculated center of gravity of the machine, which meant it was bolted to the back of the crank· case. This meant that tbe forces were thus transmitted to the most perfectly balanced center point of the bike, but the trou ble was that this was so far from the final drive pinion that a two-piece drive shaft was now reo quired, with a universal joint coupling the two halves. Testing appeared to indicate thalthis would hold up in use, so the learn heaved a sigh of relief and got down to completing the detail work before the bike's rac· ing debut at Paul Ricard in southern France. Engine development had concentrated on yielding a wide and usable powerband rather than aiming for maxiumum borsepower, but even so the dyno sheets wbich Massimo sbowed me indicated that with usa· ble power coming in as low as 4,000 rpm, a maxiumum power figure of 140 borsepower at the rear wheel at 11,800 rpm was obtained witb the camshafts employed for the Bol d'Or. In the interests of reliability, it was decided to tune the engine so as to produce a little less power but at reduced revs, and tbe report of the final dyno run on September 4, 1978, ten days before the Bol d'Or, shows the engine which was employed for the race yielded U8.7 horsepower at 10,500 rpm, with maxiumum torque of 95.5 Newton meters at 9,500 rpm. It was an exceptionally smooth and easy engine to race with. Weight was, however, a handicap, because it bad been decided from the outset not to employ expensive magnesium castings and titanium com· ponents while the bike was still being developed, especially as these could have no relevance for the future in terms of lessons to be incorporated in road bike production. Thus while the complete bike scaled 524 pounds ready to race with oil, water and half a tank of fuel, of which the engine/· gearbox unit alone represented ~85 pounds, Massimo Laverda stresses that with the use of lightweight materials this could have been slashed to around 418 pounds fairly readily. "All it would have taken was money," he said as he grinned. With a wheelbase of 57·inches and seat height of only 29·inches, the bike was as compact as any of its rivals, and at just under 21·inches across at the widest point of the fairing, in spite of the 9O-degree cylinder angle and twin radiators, it was actually narrower than many of tbe Japanese fours running in the 801 d'Or that year. Campagnolo mag·a1loy wheels with Dunlop slicks were fitted to the bike for the race, coupled with twin 280mm Brembo cast iron disc brakes at the front and a single 2~Omm at the rear. The front fork was a ~8mm Marzoc· chi unit. In the race, it was the one part of the design which the team was less than lOO-percent confident in which let them down: the drive shaft univer· sal joint broke after eight and a half hours of what amounted to a destruction test of this untried component. "We could have fitted another," says Massimo, "and kept going, but it wouldn't have proved anything. We bad all the other data we needed from the outing and it would only have gone again, perhaps at a dangerou moment for the rider." So the bike was retired, but nOl before it had proven the eHiciency of its engine by recording an eye-opening speed of 175.46 mpb through the speed trap at the end of the mile·long Mistral straight. That was 18 mw faster than the next fastest four-stroM• and even faster than the Pons/Sarron Yamaha TZ750. "With increased revs and different gearing, we could easily have exceeded 186 mph," said Massimo confidently. And you have 10 believe he's right. Sadly that was to prove the :/J Laverda's one and only public appea~ ance on the track, for at that time the technology and materials to solve me drive sbaft problem simply didn't exist. [ronically, since then, ZF inGermany has perfected an omosynetic joint design for use in Formula One racing cars, and this would alm~ certainly have cured the Laverda's problem. But by then the decisiOB had been made to retire the bike to lhe. factory display area, and employ tge lessons learned from building a~Q running it on the company's nex,( generation or' production motorq-des, beginning with the RQ-S announced last year which has· wait for it . a 120-degree crank instea(1 the previous 180·degree two up/o~ down throw of its JOta three·cylinder predecessor. And when the new range of water-cooled Laverda fours appears next year, they'll be ample proof that construction of one of the most exotic. unusual and admirable racing motor· cycles of all time really did enable Moto Laverda SpA to improve the breed. • I.... . .... _.. _..