Yoomee AFR

Yes – totally and utterly dreaming. Welcome to the mad world of John Hulme and the one active brain cell that’s still working – just!

Growing up as a young kid around the world of Mick Andrews most certainly had its benefits. First and foremost, a quick word from my father Ron into the ear of Mick’s father, Tom, resulted in a ride on the prototype Yamaha models he was developing in the ’70s. First, we had the very early Yamaha with the ‘Autolube’ and ‘Torque Induction’ before the arrival of the single rear shock absorber ‘Cantilever’ model with an engine which sported a very early form of fuel injection, albeit by a vacuum pump system. There was even talk of a semi-automatic gearbox in the form of a variable belt-driven gear system, very similar to the very early DAF cars; who remembers them?

All these ideas – apart from the DAF gearbox system – eventually made their way into production machinery, even as late as the ‘Noughties’. It brings me around to the acquisition of Gas Gas by the KTM group, which also own Husqvarna.

The big question is, will we see, in 2022 or maybe even later down the line, a completely new KTM-influenced Gas Gas trials model arrive that will once again change the face of the trials motorcycle? With my brain in overdrive, I delved into my vast collection of motorcycle sales brochures to find the automatic gearbox Husqvarna models from the ’70s; who remembers, or even rode one of them; what happened to the futuristic ‘new’ Ossa trials project that came to life in late 2010? If my mind serves me correctly, the Ossa project ended up under the Gas Gas roof in 2015 when production of the green machines finished. So where did all that technology disappear to?

WHY CHANGE A PROVEN PRODUCT?

We had a look back at the original KTM trials project back in the ’70s in issue 79 of Trial Magazine which resulted in a lot of calls from readers. They remembered the KTM trials machine and reminisced on how much they would have loved to have seen a production run and to purchase something different from the run-of-the-mill Spanish machines that were dominating the trials market. As a manufacturer, Gas Gas has a strong sporting heritage and, my guess is, that KTM will want to carry the ‘red’ brand into the future; but why change a proven product which they know they can sell?

With the introduction of the compact lightweight engine, with diaphragm clutch in the new ‘Pro’ model, they set the benchmark around 2002; everyone wanted that engine. So, what would my dream ‘Yoomee’ trials machine of the future look like? Let’s take a brief look.

AUTOMATIC GEARBOX

I still remember my father questioning Mick about a variable, or form of automatic, gearbox he spoke about. Just imagine the scenario of a very long gear which would increase and decrease the ratio with the twist of the throttle. Maybe modern technology, with electronic influence, could work; look at the gearbox setup in modern F1 cars? The Husqvarna automatic gearbox had fewer working parts than a manual one, and it proved very reliable. It automatically sensed the change in riding conditions and changed gear. Rider reports back then stated that it worked very well but at times was a little unpredictable. Wind the clock forward to more modern times, and maybe it would work while also offering a reduction in overall weight.

FUEL INJECTION

It is, in my opinion, a must-have to improve all machines as we move into a ‘Green’ world that requires emissions to be controlled.

The mechanical calibration of a carburettor will never be as accurate as an electrically-controlled one. It was first introduced on the four-stroke Cota 4RT engine, and I believe that the winning combination of man and machine, Toni Bou and the Repsol Honda, is in part due to the fine engine tuning of the four-stroke engine through the EFI system.

As the official UK importer for Ossa machines, Nigel Birkett understands the workings of fuel injection on a two-stroke better than most; he was a huge fan of it on the Ossa two-stroke. I tested the Ossa for the magazine, and the carburetion was as near to perfect as you can get. No ‘loading up’ just nice and clean, reliable carburetion at all throttle openings.

In my opinion, this is one of the strongest points of the new generation Vertigo machines. They have mastered the art of making a twostroke engine work while putting the air inlet for the engine in the best and highest possible location. Put good, clean, quality air into a two-stroke, and it will perform at its very best and also keep the cylinder barrel in excellent condition to perform at its optimum.

REVERSE CYLINDER

I was very impressed with just how compact Ossa had made the whole engine package while including all that was needed for it to work. Whether or not the reverse cylinder technology is necessary, it added a little ‘Moto GP’ feeling to the whole trials project.

The exhaust system was a strange setup and looked a little like an afterthought. Because the engine package was so good, and the overall balance so neutral, it allowed the rider to utilise the suspension package to his benefit.

With the whole machine and engine configuration changed on the Ossa, with the fuel in what was basically the front downtube; it was, if you like, a new-generation machine. The early engines suffered from a gearbox fault. Once modified by Nigel Birkett working with the Ossa engineers, it was eradicated before the project folded in 2015. The ‘cassette’ gearbox was a work of art, so simple and easy to change. The irony was that 2015 was the 75th anniversary of Ossa as a motorcycle manufacturer.

SO, WHAT’S THE FUTURE?

Publishing this article during the COVID-19 pandemic, who knows what the future holds for the sport of motorcycle trials with regards to machine development. As opposed to the machines getting more complex with advanced technology, they could go back to possibly being simpler, less sophisticated machines. As we have seen, TRRS has introduced the electric start mechanism to their trials models which, if we are honest, has been a request from the buying public for many years; it certainly transformed the Enduro market.

My other thoughts are obviously electric power. Could we see a compact hybrid twostroke electric machine? Just remember, with the acquisition of Gas Gas the KTM group have an immediate winner with the TXT-E model. This machine has won three consecutive FIM World Trials Championships, and maybe it’s just the financial difficulties at Gas Gas, that has kept it away from the buying public. As my wife, Jane, shouts to tell me the tea is ready, I am woken from the dream and dropped back into the real world. Was the ‘Yoomee’ trials machine a dream? Let’s wait and see.

It was a life-changing moment for motorcycle trials development when Mick Andrews won the 1974 Scottish Six Days Trial on the Yamaha. It was the first win for a Japanese-manufactured motorcycle and the first for a single shock absorber machine.

In the mid-70s Husqvarna introduced the automatic gearbox Motocross and Enduro models to its off-road range.

All these years later the ‘Cantilever’ Yamaha YZT 250cc from 1974 looks very futuristic.

The fuel injection on the Yamaha which used a May Pump.

With fewer working parts than a gear lever change manual gearbox, the automatic offered a weight saving.

Ossa trials machines await completion on the production line.

In 2012 Ossa had a vision of two new exciting off-road models.

This Husqvarna brochure shot shows the simplicity of the automatic gearbox.

Still a best seller: the latest Gas Gas TXT.

The removal of five bolts was all that was needed to change this superb piece of engineering: the cassette gearbox assembly on the Ossa.

To train the Ossa technicians, a cut-away engine was used to educate them.