The importance of a quality tensioner
The transmission mechanism of Buell XB is quite simple, made by two pulleys, one connected to the crankshaft and one connected to the rear rim, and by a toothed belt, whose task is to transmit the rotary motion of the driving wheel, the front pulley, to the driven wheel, which is the rear pulley.
The front pulley is never in axis with the swingarm pivot, except for some prototype motorcycles, so the overall length of the toothed belt should change during the wheel travel, becoming maximum when the front pulley, axle of the swingarm and rear pulley are aligned.
This type of mechanism let the belt stretch at the moment of maximum extension, but it is not tense during the rest of the vertical movement of the wheel. Longer is the swingarm, less is the effect for the same run of the rear suspension.
The fact that the belt is not always tense in the same way, generates some problems in term of regularity during the march. If it is not tense when we accelerate, the engine increases the number of revolutions and consequently the inertial effect relative to its rotating parts. At first, due to the recover of the belt’s game, we feel a push on the wheel proportional to the increase in the number of revolutions of the engine, then, once the toothed belt is completely taut, the whole engine torque is roughly transmitted to the rear wheel, giving us that whiplash effect that affects the driving pleasure.
Therefore, games too high give origin to little fluidity and a guide that is usually defined as “torn”. On the other hand, excessive tension leads to a very high effort on the toothed belt itself and on all the rear wheel and gearbox bearings. An exaggerated tension of the belt would bring it to stretch in a short time, requiring maintenance: moving the rear wheel of the bike, thanks to the registers that are present in every motorcycle, would consequently make the wheelbase longer than before. This would make the bike less reactive and more difficult to ride, moreover, an excessive lengthening of the toothed belt requires a replacement of it together with the rear pulley and the front pulley, which get damaged with the belt itself, requiring an expensive replacement in terms of time, work and materials.
To overcome all these problems and allow greater longevity to the belt, FreeSpirits offers you a dynamic belt tensioner, which aims to keep always a light tension on it, so as to avoid sudden tears or irregularities during the ride, without overloading the wheel or gearbox bearings, or the belt itself.
This dynamic belt tensioner adapts itself to any condition of tension, thanks to a specially sized spring. It sets the goal of maintaining a constant tension, limiting its intervention when the toothed belt is normally tensioned and intervening more decisively when the belt is too slack.
Quick and easy to mount does not require any modification.