On the move: OSSA 250 Trial MAR

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On the move: OSSA 250 Trial MAR
Jahn

On the move: OSSA 250 Trial MAR

Werner – rock hard

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Trial legend Mick Andrews crowned OSSA’s successful streak with two European Championship titles in the early 1970s and helped the Catalans to obtain a popular large-scale replica.


Jahn

Werner "Mini" Koch during the typical use of the OSSA 250 Trial MAR.

Trial, enduro, motocross – off the beaten track, the Spanish motorcycle manufacturer OSSA was right at the front. The first 125 OSSA was launched in 1949 "Plenty" rolled off the belt. The engineer Sandro Colombo laid the foundation stone for the successful enduro and trial machines. In 1963 he designed a single-cylinder two-stroke engine, the basis of which was installed in all off-roaders until OSSA’s demise in the mid-1980s.

The models from the 1960s and 1970s show that trial and enduro machines were based on the same concept. What is now an impossibility was common practice in the post-war period, because end-Europeans and trial sections differed little. In complete contrast to the current, more than questionable trend, in which enduro competitions are mutating more and more into motocross and the trial specialists jump up vertical walls from a standing start.

Forty years ago that wasn’t an issue. Therefore, it was not only the OSSA engineers who turned a competition enduro bike into an agile trial motorcycle with just a few changes. Most important point: Tamer control times, smaller carburetor cross-sections (27 instead of 33 mm) and slim exhaust pipes with long, cylindrical manifolds trimmed the engines for pulling power: just 18 HP at 6000 rpm are for the trial 250 in the brochure; the Enduro 250, type E 73, was specified with 28 hp on the rear wheel. The extremely long gear housing is typical of the engine designs of that time.

The distance between the output pinion and the swing arm bearing is so large that the lower chain strand requires a spring-loaded tensioning rail. It is a shame that the designers did not consistently transplant the extremely compact and short engine of Santiago Herrero’s road racing machine into their off-road models. With this design you would have been years ahead of the competition. Ultimately, this adherence to antiquated technology was the decisive factor for Mick Andrews to say goodbye to the Spaniards and to dock with Yamaha in 1973.

The spring travel of the Trial 250 only had to be shortened by a few centimeters compared to the enduro models, which is why the design of the fork and shock absorber were identical, and only the coordination of spring rate and damping was adjusted. In order to gain ground clearance for the trial machine, which weighs just under 90 kilograms, without increasing the overall height, the tubular steel beams in front of the crankcase were cut. The motor hangs in the frame that is open at the bottom. An aluminum sheet, tightly molded around the crankcase, protects it from stone chips and slipping.

A small seat roll serves as a bench, after all, trial riders only demonstrate their art while standing. Change of scene. Sunday morning in December 2008. The citizens are still in their springs, only a few colorfully dressed people are calmly handling antiquated motorbikes on the trial site in Sulz am Neckar. A few liters of fuel gurgles into the small tank, the spray cock opened, the kick starter kicked – but the engine does not start. The float chamber is emptied in no time at all; Fluffed cheeks clean the nozzle holder with "Compressed air", a lighter dries spark plugs. Then another kick, and the OSSA engine gasps blue clouds in the cold winter air, splatters a little rotten and overly greasy. Helmet on, full throttle up and down the dirt road, and the two-stroke engine has burned itself free.

Classic trial in self-experiment


Jahn

Double swing arm with twin shock; large sprocket for short translation.

"So now you." My old specialist Nobby pushes the wide handlebars into my hand and grins. He knows very well that my last excursion on a trialer was a good 20 years ago and thought up a nice round for me. "Very easy for the beginning: the sloping slope around the tree. Then down into the woods to warm up, then over to the rocks to climb." Nobby has a good laugh and is fed up with training since he added the Mick Andrews replica to his classic enduro fleet of Honda CB 250 Scrambler and Yamaha XT 250. And it is not intended as a piece of jewelery, but as a base for classic trials. "Little effort, lots of fun", Nobby comments on his passion for the old iron. "If it doesn’t brutally hit you in the rocks, nothing will break. And with five liters of the mixture, you will get sore muscles while exercising."

So, and now me. Even if you’ve mastered the most incredible motorcycle adventures together, you don’t want to be naked in front of old friends. Also because the third party, the photographer, is also one of the companions from the enduro era. What doesn’t change the fact that the gentlemen viewers relish unpacking their jokes before the first tense U-turn on the sloping slope. Whereupon the knocker can only bring his high-tech camera out of the line of fire of the crackling lumps of clay with difficulty. armistice.

But where he is right, he is right, the clippers: trial driving is unique because the stabilizing effect of the wheels is lost due to the lack of speed. The first exercise belongs to the simple balance between man and machine. How did that work again in the past? Put the front wheel up, gently at eye level on the tree trunk and stand still – casually, for minutes, as if nailed to the ground. After the fifth attempt and a rough ram that almost uproots the tree, I turn to more dynamic locomotion: turning at the steering stop, for example. No problem with this engine, because it continues to run even if the piston only heaves itself with difficulty above TDC. "Disengaging is frowned upon in the classic trial", Nobby explained to me.

After half an hour of practice, the old reflexes and the sense of balance slowly come back. Fortunately, the OSSA is still one of those trial machines that was built to be good-natured. When you climb over clay-smeared rock and the super-soft Michelin Competition X 11 tire suddenly bites into the rock, modern, aggressive trialers just throw you off. The OSSA briefly lifts the front wheel and gently pushes you over the obstacle. Such friendliness increases the desire for more, for higher, for steeper.

You can forgive the MAR 250 that it pushes violently over the front wheel on smooth forest ground, skids on the floor plate when it comes to knee-high rock edges and, when it comes down to it, hangs a bit on the gas. In return, it gives a returnee from the first meter the feeling that the rider is in charge. This is probably one of the reasons why more and more classics fans are thinking back to the so-called twin shockers and are finding joy in trials again. Should I find a suitable device in the near future, Nobby will have competition. Because I still have some time until I retire, my friend.

Technical specifications; Classic trial events

OSSA Trial 250 MAR

Engine: air-cooled, slot-controlled single-cylinder two-stroke engine; Mixture lubrication 1:20, bore 72 mm, stroke 60 mm, displacement 244 cm³, compression 8: 1, 18 HP at 6000 rpm, mixture preparation slide carburettor, Ø 27 mm

Electrical system: Kick starter, contactless Motoplat thyristor ignition, alternator 6 volts / 34 watts

Power transmission: Multi-disc oil bath clutch, dog-shift four-speed gearbox, gear ratio 4.31 / 3.24 / 2.40 / 1.0, secondary drive: chain

Landing gear: tubular steel frame open at the bottom, hydraulically damped telescopic fork at the front, two-arm swing arm with two hydraulically damped spring struts at the rear, spring travel front / rear 122/122 mm, wire-spoke wheels with aluminum rims, front tires 2.75 x 21, rear tires 4.00 x 18, front and rear simplex drum brakes, Ø 120 mm

Measurements and weight: Weight 88 kg, tank capacity 6.25 liters

Manufacturer: OSSA Motorcycles, Barcelona / Spain

Anyone who wants to know it again is warmly welcome to the classic trial. Two series are officially running in Germany: Die Deutsche Trialsport Gemeinschaft e. V. organizes the Classic Trial D-Cup (www.ortwinsann.de); Friends of motorized scrambling can also take part in the Hanse Classics (www.hanse-classics.de). No DMSB license is required for either event. The competition conditions are subject to the respective organizers, who aim to ensure that the entry fee does not exceed 15 euros. The Classic Trial Euro-Cup has established itself across Europe; however, regional trial and motorsport clubs often organize exciting classic trials as part of their club championships.

So that the machine material is really classic and not just looks like it, the machines are divided into categories: On the one hand, four-stroke machines start with divided engine / gear units, the so-called 65 pre-units, and the 65 units with one-piece engine / gear units. Both "Twin stools" it is a two-stroke with a conventional spring system, ie two struts, built from 1966 onwards "Mono stool" are two-stroke trial machines with standard central suspension and are only allowed out of evaluation.

Technical and visual changes to the classic trial machines may only be made if they have been converted with contemporary material and the look that was common at the time. Water cooling and disc brakes are generally not allowed. In order to take into account the wide range of driving skills, up to five lanes of different weight are available. These are color-coded and must be selected before starting. As is customary in trial sport, so-called track supervisors monitor compliance with the rules.

Anyone who would like to find out more about other events, dates and the technical regulations can do so on the one hand via the DMSB or, even better and more up-to-date, on the homepage of the Trialsport magazine at www.trialsport.de.

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