A quiet Ducati clutch, the easy way!
By Nick Woods
The following modification is based on my experiences with a ‘99 ST4 clutch, initially using an OEM basket and centre/hub plus an aftermarket plate pack, and subsequently an OEM centre and Charlie Smith/Procutting clutch basket with matched Barnett plate pack.
It also works very well on a Cagiva Gran Canyon (904 Ducati motor) that had a rather loud clutch rattle as received.
Other members of the Yahoo (now Groups.io) LiST have tried it with success, but we have not researched into whether it can be applied to every possible combination of OEM and aftermarket components. It is important, therefore, that you understand the principles before starting work. As with any modification, there are always pros and cons, so you do it at your own risk!
Ducati’s dry clutch has good ‘feel’ and works well, its one main advantage over the wet clutches of other manufacturers being that dust from the friction linings does not contaminate the oil. Theoretically, the absence of friction-reducing oil might also make it possible to use lighter clutch springs, but no Ducati rider has ever seen evidence of that! Given there is no need to keep oil inside the unit, it can be run open to cool it and give it a racier look, but that is when its major attribute becomes really evident. It is loud!!
Not a problem when the engine is actually driving the rear wheel, a heavy knocking noise is apparent when idling in neutral, and is sufficient to be quite offensive to those of a sensitive nature. (We shall ignore riders who proclaim that ‘loud clutches save lives’, as they are confused souls…) Whether the noise is objectionable or not, that mechanical mayhem does no good to the clutch itself, such that some owners prefer to ride the bike gently as it warms up, rather than let the clutch hammer itself apart.
The noise is directly related to the dry status of the Ducati clutch, as there is no oil film to cushion necessary play in the unit. The infrequent and uneven power pulses from the beloved vee-twin also make it worse than would be the case with a four-cylinder engine, plus the Ducati is sports-orientated and does not carry a massive flywheel that would damp the pulses better.
The knocking actually comes from the clutch plate-pack rocking to and fro in the slots of the clutch basket. The closer the clearances, as with the fabled Charlie/Barnett set-up, the quieter the unit, and having alloy tabs running in alloy slots is less resonant than with the original steel on steel. However, sooner or later, the clearances will open up with normal wear, and the knocking starts in ernest.
Several commercial suppliers have hit on a method of preventing the to-and-fro fretting of the plate-pack in the basket, and the method outlined below is based on personal experience of one of them which utilised a special plate pack mated to the OEM ST4 basket and centre. The difference with the quietening mod that follows is that it requires nothing more than the addition of one or two old friction plates, and no machining or special components at all.
Basically, it consists of incorporating the equivalent of a rotary friction damper to bind the entire clutch unit together, (centre, plate-pack and basket) when the clutch is fully engaged. It has no effect on clutch action, but there are some theoretical mechanical/wear disadvantages that possibly explain why Ducati themselves have not adopted it, though there is some evidence that they did utilise it at one stage of 900 production, perhaps also with the Paso, but they subsequently abandoned it.
I’ll outline the theoretical disadvantages later but, rest assured, clutches modified in this way have given many thousands of miles of trouble-free silent service.