The Sanglas was looking beautiful, it was hard to believe that it was the same bike that a month ago had aroused my curiosity, without a doubt the effort was paying off. At first glance, there was little left to do, however as you delved into the details, new problems emerged, possible improvements, and a maxim that was repeated over and over again: every day we fix something, something new breaks down.


However, the time had come to take her out to the street, to remove the cobwebs from the engine. We already enjoyed each day with its sound from another time, we checked that each turn signal, light, horn or any electrical element that came on, continued to work, even if we had tried it ten minutes before, however we could not ignore the largest of the problems. The motorcycle started but did not work .

Of all the problems we had encountered, this was one of the simplest when determining its causes, however it was possibly the most difficult to solve, with our means and knowledge. Let me explain: the engine was working, that was obvious, as I said, we listened to it every day, however, the moment we put in any gear, the bike crashed. We had a transmission problem, we had the power, but not the way to transmit it to the wheels, and the clutch and gearbox take care of this in the first place.

When a vehicle does not start, or stalls as soon as the speed is put in, the average Spaniard opts for the well-known universal solution: starting down the hill in second gear . This complex solution has the trade-off of having to push the bike uphill if the method doesn't work, and this was obviously the case. If we add to this that we had not yet reached the chapter on brakes, the matter could turn into a drama.

Neither short nor lazy, my father went downhill with the second gear engaged, started the motorcycle and effectively managed to scratch a few meters of traction, but when he reached the end of the slope and tried to move forward again, the motorcycle, a machine with fixed habits , he stalled again, and we had to push his 400 kg all the way up again.

The effort, however, had not been in vain, since we could determine that the gearbox, at least the first and second gear, existed and engaged, even by force. The problem was in the clutch .


Operation of a Sanglas clutch

The clutch connects the engine with the gearbox, it is responsible for allowing the change of gears. The piston goes up and down inside the cylinder continuously, we can make it go faster or slower using the accelerator, however it never stops completely, unless we stop the engine.


Let's imagine, for simplicity, that the rising and falling piston rotates a toothed wheel that transmits the movement to the rear wheel of our motorcycle. When changing gears, we change the size of said sprocket, the first the smallest, up to the fourth gear that the Sanglas mounts, the largest wheel. If the engine never stops, how can we change the gear without blowing it up? Thanks to the clutch.

It is not my intention to stop and explain its mechanics in detail, but I think that with a simple example you can understand well how the clutch of a motorcycle works.. What we want to achieve is that one part always turns (the shaft that comes from the motor) and another part can be stopped to change the gear (the gear shaft). Let's imagine a blender, in the kitchen, preparing any emulsion. In this case, the mixer is the motor, it always turns, and the glass is our gear axis, it is stopped while the mixer turns. As long as the emulsion is liquid, we can even release the glass, which will remain standing while the mixer turns. Right now the engine is spinning and our shift shaft is stationary, so we could shift gears without a problem. As soon as the mixture emulsifies, its density will make the mixer and the glass, taken to the extreme, rotate jointly. At this moment we have our engine turning together with the gearshift, and therefore, our motorcycle in motion!


In the clutch, this occurs thanks to the so-called brake discs , which "drag" metal discs that make the shift shaft rotate. When we actuate the clutch, these discs separate and stop dragging the metal ones, so the gearshift can stop.


Here you have a video of the operation of the La Lebrijana clutch , you can see how at the beginning, the clutch rotates jointly with the motor shaft, however, at the end, when the discs are separated, the clutch rotates but not the shaft.


At this point in the repair I have to say that we lacked courage and the desire to get oil stained. We had detected the problem and we sensed the solution, but we did not know what we could find when opening the engine, we were afraid we would lose a part and enlarge the problem. So, to my regret, we decided to take the Sanglas to a well-known mechanic. Fortunately, she had the workshop down the street, so we didn't have to carry her up the street again.


After the time we had spent with her, we could not even leave her at the mechanic, who without problem let us observe and ask while he repaired the clutch.

The problem was solved by separating the discs, which over time, lack of use and the bad condition of the oil, had become stuck, making it impossible for the clutch mechanism to function. He cleaned them with a special non-acid clutch degreaser .

In the example above, the mixture would have emulsified and the mixer would always drag the glass. In the photo you can see the green color of the oil, completely decomposed.

The truth is that I spent a whole weekend visiting the mechanic to see if he had finished with the Sanglas, but there it was, with the engine open without repairing, as if complaining about having left it there abandoned. Finally, after a long wait, we were able to pick it up from the workshop, and this time the bike was working, we didn't have to drag it up the street. The Primitiva was already flying and we had learned the operation of a Sanglas clutch.

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