The 620 is the perfect entry in the Monster family, and is available in three different versions. The most essential version is the 620IE Dark Monodisco, with its five-speed transmission and single front disc brake, it's easy to ride in style, and at a tempting price too. The Monster 620IE and Monster 620IE Dark showcase the innovative new APTC clutch for dramatically reduced clutch lever "pull" effort, and a "slipper clutch" design that reduces abrupt engagement during down shifting. In addition, they feature six-speed transmissions and double disc front brakes, quality elements that appear on the top-of-the-range Monsters.
The benefits of the APTC clutch system cannot be over-stated for the novice and expert rider alike. Clutch "pull" effort has been reduced by an incredible 40%, making operation less of a task. Furthermore, during rides in congested cities where constant engagement and disengagement of the clutch is required, the light clutch lever pull is a pleasure.
The newly developed clutch -named the APTC (Adler Power Torque Plate Clutch) -used on the 2004 Monster 620 and 620 Dark is patented and designed by Adler, and developed according to precise specifications by the Ducati R&D Department. It is a clutch with follow-up torque: this means that the torque transmitted is always a function of the torque applied to the device.
This feature has made it possible to dramatically reduce effort required to disengage the clutch via the clutch lever, while still ensuring excellent operation and high dependability. Thanks to the APTC device, the torque transmitted is increased significantly compared to that of a conventional clutch, without having to increase the size of the clutch itself. Another important characteristic is that the system automatically limits back torque that is generated during heavy braking and down shifting, avoiding rear wheel skidding. In addition to these obvious advantages, the APTC clutch does not require did not require any adjustment or changes to the original clutch case or the primary drive system.
The R&D Department at Ducati has worked alongside Adler R&D to develop an innovative clutch, in line with the new technological and performance-related goals of the modern Desmodromic Ducati engines. The objective was to obtain high torque, without increasing the size of the clutch, and simultaneously achieving more control and lower handlebar clutch lever effort. A unique technical solution has allowed the creation of a clutch in which the transmittable torque is, in part, independent from the pressure of the clutch springs.
In a conventional clutch, with the same size discs and made from the same material, the transmittable torque can only be increased if the pressure of the helical springs that act on the pressure plate is increased. However, increased spring pressure creates a negative effect, as the effort required at the handlebar lever is also increased.
Eliminating the risk of "back torque" and rear wheel skidding
If you approach a turn at steady speed and you downshift a number of gears in rapid succession, the moment you release the clutch lever, rather than the engine driving the rear wheel, the opposite occurs and the rear wheel is driving the engine. In this case, the torque is not transmitted from the crankshaft to the rear wheel, but the exact opposite occurs.
In this situation, the torque is technically defined as back torque and it is a characteristic of twin engines in particular, which possess strong engine braking.
The effect of this phenomenon is twofold:
1. The rear wheel of the motorcycle tends to skid and consequently loses traction.
2. The engine is driven faster and risks potential over-revving.
With the APTC device, Ducati has eliminated these two risks.
Less pressure, the same torque
The APTC clutch used on Ducati engines of 620cc and greater has allowed a reduction of the diameter of the clutch discs from 150 mm to 140 mm, and considerable volume reduction.
At the same time the effort that must be applied to compress the helical spring of the pressure plate has been reduced from 860 N to 560 N, while the maximum torque that can be transmitted (9.98 Nm) remains the same as in a conventional clutch. The lighter pressure helical springs, which act on the clutch pressure plate, produce notably lower effort required at the handlebar clutch lever, and consequently improved clutch control. In addition, the effects of the back torque, rear wheel skidding and the tendency of the engine to over-rev while going down the gears have been brilliantly eliminated.