Yamaha SR250 Alpina
The donor bike used in this build is the very well-known and for many years ubiquitous in our country, the Yamaha SR250, in its Custom version called Special. It was called "the motorcycle of the messengers" since at the time this group made it their work tool due to its infinite virtues: low fuel consumption, bulletproof reliability, more than acceptable features for city conmuting and intercity trips, comfort and price The single-cylinder four-stroke is a version of an engine that Yamaha took advantage of over and over again for the virtues mentioned above in models like the XT350 and many other motorcycles in markets often opposite to ours as the USA market (Exciter). There is, therefore, an almost infinite availability of units and spare parts, even if we are talking about a motorcycle with several decades on its back.
However, the SR250 "per se" never had an Off-Road version, in a country like Spain where Off-Road bikes were the core of the manufacturing motorcycles with brands like Ossa, Bultaco and Montesa in the 70s decade.
With this idea in mind, we decided to use a base as available and cheap as the SR250 Special to pay homage to the golden generation of Spanish offroad motorcycle manufacturers. Immediately and taking into account the characteristics of the donor motorcycle, the Bultaco Alpina came to our mind, a motorcycle designed with no other desire than to take a quiet ride through the mountains, without tackling steep trial roads or "flying" through fast . enduro or motocross dirt tracks.
To achieve the line of the Bultaco Alpina, several key points arose, especially starting from the SR's Special version - clearly Custom style - of the Yamaha: a larger diameter rear wheel - 17" compared to the 16" of the donor bike - a low and flat handlebar, a harder and higher rear suspension and a fuel tank with the characteristic look of the Bultaco.
Although the first three are relatively easy to achieve, the issue of the tank was much more complex than it may seem at first glance. We got hold of an original Alpina tank, but as soon as we considered it, it was clear that it was impossible to straight adapt to the Yamaha frame, due to the size and shape of the tunnel tank, the tank holders, etc. which left us no other option than to do it completely from scratch and to measure. Using the original Bultaco tank as a mold for the lateral and upper surfaces, the Yamaha tunnel made of fiberglass was attached directly to the motorcycle. With the tunnel ready, many hours of work with the fiberglass until the final shape seen in the photos was achieved. The position of the fuel tap was also changed to the opposite side - rightside instead the stock left side - to leave the starter puller free play on its original side and some room for the new exhaust pipe. All this bearing in mind that the current Spanish legislation does not allow hand made fuel tanks.
It is just the new hand made stainless steel exhaust, which flows under the seat, which definitely allows us to match the look of the old Bultaco 2S, taking it to the opposite side of the donor bike and sticking it as close to the engine as possible. The muffler shows just a bit under the seat and rear fender, behind the gas shock absorbers, making the bike closer to old trial bikes due to its narrowness.
The frame has been chopped at the back and the new seat also serves as a fixing for the tank, painted matching the colors of the original Bultaco Alpina.
Finally, and to give the bike an even more "retro" look, we proceeded to install the kick start. The SRs sold in Spain - and this is no exception - had an electric starter only. However, as we explained at the beginning, this engine shares a large number of parts with other models that included the classic kick start.
Polished aluminum fenders and knobby tires add the finishing touch to this beautiful and fun SR250, a tribute to the golden age of Spanish motorcycle manufacturing.
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