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Trials Motorcycles, a Short History

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Trials bikes are specialized off-road machines.

This wasn’t always the case; when trials started in Scotland before 1910, riders used regular machines, usually the common four-stroke singles. There wasn’t the degree of specialization of motorcycles that we have now. The bikes then were suited to the trials events of the day-, which were basically hillclimbs-with lots of low-end power and large flywheels. The flywheels and soft tuning allowed for plenty of ‘plonking’ power to creep over and around obstacles, and the four stroke bikes had plenty of traction.

1960s

As trials became more specialized, the bikes improved along with the events. Or perhaps the events became more difficult as bikes improved. Whichever, a milestone in the evolution of trials machinery was Sammy Miller’s 1960’s factory Ariel HT5, known as ‘GOV132’ after its license plate number. Sammy lightened the bike and changed the steering head angle to get quicker steering. The result was a bike that went over obstacles better and could do tighter turns.

Miller’s success with the Ariel was noticed by his competitors and by the makers of competing machinery, including AJS. Soon others were shaving weight off their bikes. Sammy was hired by the Spanish company Bultaco in the mid-60s. Bultaco was successful making lightweight two-stroke machines for street and road racing and wanted to move into trials. The modern two-stroke trials bike was born from Sammy Miller’s work on the Bultaco.

1970s

Other Spanish manufacturers, always competitive with Bultaco, started working on trials bikes of their own. Soon the trials loops of the world were filled with Bultacos, Montesas and Ossas, all making rattly two-stroke sounds and castor-oil smoke while doing obstacles that riders of the heavier four-stroke machines could only dream about. Mick Andrews, another British trials legend, helped develop the Ossa. Trials boomed in many countries, especially the United States. Motorcycle magazine editors predicted that trials would be "more popular than motocross."

In 1973, expecting the trials boom to hit any moment, Honda introduced the first Japanese production trials bike, the four-stroke TL125. Yamaha, Suzuki and Kawasaki followed a year later, and a Honda TL250 arrived in 1975. The Japanese bikes did not handle quite as well as the Spanish bikes, but were reliable and could be made to handle well enough. The Japanese makers followed the Spanish company’s tracks and hired some of the big names in trials to help develop their bikes. Mick Andrews went to Yamaha and worked with them for many years. Honda hired Miller away from Bultaco and he helped them develop their TL250, first by making a lighter frame with more ground clearance, then with advice on the factory’s expensive magnesium and titanium RTL competition models.

1980s

In 1979 and 1980 the Spanish companies suffered from labor strikes and walkouts. The USA trials boom had never come and Spain was beset with economic problems. The championship Bultaco factory team with newly-crowned World Champion American Bernie Schreiber was forced to disband mid-season, with each rider finding a home on a different make. The reign of the Spanish manufacturers ended and some Italian makes picked up the slack. SWM, Italjet and Fantic started volume production and started supporting riders, and winning, in the early 80s. Honda went to Europe with even more advanced four-strokes to contest the world rounds and won two championships under Eddie Lejune.

At this time, the bikes were of the same basic design that Bultaco pioneered in the late 60s, albeit refined with slightly lighter weight, better power and slightly longer travel suspension. But the huge suspension revolution that had occurred with Motorcross machines in the mid-70s had little effect on trials machinery.

That changed in 1984 when Yamaha introduced the new monoshock TY250. Having no parts in common with the old 1974-design TY, the new TY’s centrally mounted shock, low seat and longer travel suspension revolutionized trials bike design. The other manufacturers leapt to follow suit, with other monoshock models coming out a year later. At this point, the major manufacturers were Yamaha, sole Spanish survivor Montesa, Italians Beta and Fantic (SWM and Italjet having ended their fling with trials). Yamaha didn’t sponsor top riders but their new TY Monoshock bikes were very successful in club events.

1990s

In the last decade, Beta and the Spanish Gas-Gas Company have pushed trials bike design forward, with disc brakes, water cooling and narrow perimeter-type frames. The modern ‘stop and go’ riding style pioneered by Schreiber, LeJune and others, where riders hop the bike to get into position then drop the clutch to launch themselves over the next obstacle, affected trials bike design. Top riders demanded quicker revving engines to rocket them over larger obstacles with less run-up than before. What the World Round riders use one year becomes the production bike the next.

2000 onwards

Modern trials bike design has stabilized for the moment. A modern trials bike has a very low seat, to allow the rider to crouch low on the bike or let the bike come up farther to him when cresting a big step. Suspension travel is usually around 7 inches in the front and 6 in the rear. Damping is light, biased towards letting the bike rebound on it’s springs to make hopping the bike easier. The engines are all water-cooled two-strokes with reed-valve induction. Engine response is much quicker than the old Bultacos, making it possible for a rider to jump up a step with little or no run-up. Tires are sticky-compound tubeless radials on the rear, and sticky tube-type bias-ply on the front. Typical tire pressures are 4 psi rear and 6 in the front. The radial rear tires have flexible sidewalls to let the tread form itself around irregularities, increasing traction. Typical weight is around 185 pounds with all fluids and the usual 1 gallon of fuel on board. Gearboxes are usually 6 speeds, with three closely-spaced low gears to give the rider a choice of gears for sections and three higher gears for riding the loop (and roads where legal).

The latest developments are hydraulic clutches and exhaust power valves. The lever effort with a hydraulic-actuated clutch is not improved over cable clutches, but the hydraulic system gives the same engagement point no matter how much the clutch plates get hot and expand. The new Fantic Section features an exhaust power valve. The valve changes the timing of the exhaust port, allowing Fantic to tune the engine for good low-end power and still let it rev more than most trials bike engines.

Words by Eric Murray