After putting up with a graunching (for lack of a better term) clutch on my 750GTL for far longer than I thought my OCD would allow, I finally decided to see what I could do. I also wanted to address the still too-heavy lever action by fitting a set of springs that I had put aside from an early steel-type clutch, just to see if it would work.
While these clutches are generally vice-free with smooth action when engaged, I have come across quite a few, twins and triples, that displayed similar issues to mine.
From standstill, the clutch would emit a scrunch/graunch/groan/judder as the lever was fed in. Hot or cold was no different. Dismantling showed no obvious discrepancies, both hub and basket were still in good condition with very little wear evident in the splines. Friction plates averaged at 2.7mm, plain plates all nice and flat. Hub tight on the mainshaft, basket bush well within spec. Fairly new springs. Clutch cable and lever nicely lubed, throw-out mechanism recently swapped for the earlier "steel clutch" version (this had already reduced lever effort considerably... but not enough for my liking!). Could't find any reason why it shouldn't work properly!
I remembered working on a Ducati Bevel with a truely horrible clutch many years ago. The whole bike would judder as the clutch engaged when starting off. The clutch itself showed no signs of abuse, all components were in what I deemed to be good usable condition. Coincidently, a few days previously, I had dived into a MZ1000S clutch and came across a spring-type component installed in the middle of the clutch plate pack. This fitted inside the inner diametre of one of the friction plates and seemed to cushion the movement of the 2 adjacent plain plates. I had a hunch this could be a cure to my Bevel issue. Of course the MZ part would never fit the bevel clutch so I fitted an o-ring that was slightly thicker than a friction plate over the clutch hub inside the plate pack. The friction plate ID was sufficient to clear the o-ring. To everybodys' surprise, the clutch worked about as perfectly as one could possibly wish for! I explained to the customer that this was definitely not a forever-fix, but it was far better than before and would most probably last for 2-3 seasons before the o-ring perished to the point of renewal. He rode away happily...
Back to Laverdas. After measuring hub and friction plates , I ordered a couple of 120mm x 3mm o-rings in NBR70. The hub is around 127mm diametre, when stretched over the hub, the o-ring flattened slightly to 3.2mm width. I then machined one of the friction plates to clear the o-ring. This plate and the o-ring were fitted in the middle of the pack, all else just went back together as before. Before that, I did some quick spring calculations; the early-type springs seem considerably softer when compressed by hand when compared to the later type. Wire is 0.2mm thinner, same number of windings, OD is slightly larger, but the spring rate was still only little less to those that were fitted prior. So I made 6 little spacers, 2 mm thick, to fit under the heads of the spring retainer screws, effectively reducing spring pre-load (for the sceptics, much the same as in later triples, part # 33 111 121, introduced in the Jota 120). However, these were 3mm thick!) This brought spring pressure back into the ball park. While still nowhere near a girlie-type japanese bike clutch, lever action is now absolutely acceptable and light-years ahead of the stock set-up.
This evenings' run was the acid test. After an unaccustomed astonishingly smooth take off from standstill, the clutch behaved immpeccably! Terrific lever action, smooth take-offs with neither drag nor slippage! Needless to say, I'm very happy with the result.
BTW, this clutch has been modified to incorporate the infamous anti-rattle springs as well.
Bike is becoming more and more civilised!
piet
While these clutches are generally vice-free with smooth action when engaged, I have come across quite a few, twins and triples, that displayed similar issues to mine.
From standstill, the clutch would emit a scrunch/graunch/groan/judder as the lever was fed in. Hot or cold was no different. Dismantling showed no obvious discrepancies, both hub and basket were still in good condition with very little wear evident in the splines. Friction plates averaged at 2.7mm, plain plates all nice and flat. Hub tight on the mainshaft, basket bush well within spec. Fairly new springs. Clutch cable and lever nicely lubed, throw-out mechanism recently swapped for the earlier "steel clutch" version (this had already reduced lever effort considerably... but not enough for my liking!). Could't find any reason why it shouldn't work properly!
I remembered working on a Ducati Bevel with a truely horrible clutch many years ago. The whole bike would judder as the clutch engaged when starting off. The clutch itself showed no signs of abuse, all components were in what I deemed to be good usable condition. Coincidently, a few days previously, I had dived into a MZ1000S clutch and came across a spring-type component installed in the middle of the clutch plate pack. This fitted inside the inner diametre of one of the friction plates and seemed to cushion the movement of the 2 adjacent plain plates. I had a hunch this could be a cure to my Bevel issue. Of course the MZ part would never fit the bevel clutch so I fitted an o-ring that was slightly thicker than a friction plate over the clutch hub inside the plate pack. The friction plate ID was sufficient to clear the o-ring. To everybodys' surprise, the clutch worked about as perfectly as one could possibly wish for! I explained to the customer that this was definitely not a forever-fix, but it was far better than before and would most probably last for 2-3 seasons before the o-ring perished to the point of renewal. He rode away happily...
Back to Laverdas. After measuring hub and friction plates , I ordered a couple of 120mm x 3mm o-rings in NBR70. The hub is around 127mm diametre, when stretched over the hub, the o-ring flattened slightly to 3.2mm width. I then machined one of the friction plates to clear the o-ring. This plate and the o-ring were fitted in the middle of the pack, all else just went back together as before. Before that, I did some quick spring calculations; the early-type springs seem considerably softer when compressed by hand when compared to the later type. Wire is 0.2mm thinner, same number of windings, OD is slightly larger, but the spring rate was still only little less to those that were fitted prior. So I made 6 little spacers, 2 mm thick, to fit under the heads of the spring retainer screws, effectively reducing spring pre-load (for the sceptics, much the same as in later triples, part # 33 111 121, introduced in the Jota 120). However, these were 3mm thick!) This brought spring pressure back into the ball park. While still nowhere near a girlie-type japanese bike clutch, lever action is now absolutely acceptable and light-years ahead of the stock set-up.
This evenings' run was the acid test. After an unaccustomed astonishingly smooth take off from standstill, the clutch behaved immpeccably! Terrific lever action, smooth take-offs with neither drag nor slippage! Needless to say, I'm very happy with the result.
BTW, this clutch has been modified to incorporate the infamous anti-rattle springs as well.
Bike is becoming more and more civilised!piet
