Clutches... what's changed?

[Adam_Winstone]

So what has changed with clutches?!

Whilst I used to be able to build a fairly standard clutch (standard rear sprocket, Surflex B 4-plate, uprated springs) for a fairly standard road motor (anything from standard 125 to mild road tune iron 225) and be sure of thousands of trouble-free miles, over the last 10 years so I've run into more and more issues with clutches getting hot in use and then not releasing fully. I'm not talking about assemblies that don't have sufficient space between plates for separation, nor notched/worn components, nor bikes with insufficient travel at lever (top or bottom), rather, I'm meaning clutches that have everything correct and shouldn't be suffering from drag when warm... yet I've experienced it on a number of motors, as have a number of pals.

Please note that I've got plenty of problem-free clutches and components so I'm not asking for advice on upgrades or recommendations for a better clutch, rather, I'm just wondering what has changed in recent years to make this become an issue? Ruling out the assembly and the bike, the only thing that I can think this could be is an issue of the oil and corks combination. In all cases where I've known this to be an issue, standard ST90 and Surflex B plates have been involved. I'm aware of the old joke of the 'C' in Surflex C standing for 'crap', however, in previous years the Surflex B plates could be relied on for reasonable service!

Any thoughts on the matter?

Adam

[coaster]

Not related to rear sprocket size Adam? Also, I have just stripped the 5 plate (based on Readspeed) clutch that has been in my Avanti for a while without any bother other than dragging when warm. I found the plates to be fine but a LOT of rock in the bronze bush which I'm thinking wont have been helping the situation.

[ULC Soulagent]

I’ve changed my oil from st90 and now run exol classic mineral hd40 with no issues so far
I’d like too add that I’m only using bgm plates in my Harry Barlow 240.
Only use surflex b in my 175 setup and use St90 in that with no issues

[Adam_Winstone]

Not related to rear sprocket size Adam? Also, I have just stripped the 5 plate (based on Readspeed) clutch that has been in my Avanti for a while without any bother other than dragging when warm. I found the plates to be fine but a LOT of rock in the bronze bush which I'm thinking wont have been helping the situation.

Nope, this is an issue that is not related to wear of components, levers, lever housing, cables, lack of room for separation or other assembly issue. I'm losing count of the number of bikes that have suffered from this, mine and others locally.

It's an odd one and seems to be as though the cork plates are sticking more than they should and or are expanding much more than they should, with drag being the result. It's odd as the assemblies that I've stripped to inspect have plenty of separation room, and some of these assemblies have suffered the same even after changing out to thinner steels and/or top plate. Cable adjustment, lever swing and all the other issues that would normally be related to drag have been addressed in each of the cases.

One thing that I cannot rule out in each case is inner cable manufacture and the possibility of cable stretch in operation, which has been mooted as a possible cause, but I find that unlikely in so many cases. To me this really does seem to be an issue with oil or corks... as though something has changed

Adam

[coaster]

You are right about inner cables, that would adjust out as the cable will stop stretching after a while.

After frying a 5 plate clutch (the lever was just flapping at the top of Hardnott) on the C2C a few yeas ago I bought an AF Road clutch and its been faultless after some initial snatchiness for a few thousand miles. Very light operation, no slip and no drag on a GT240 set up. Another just fitted to the Avanti

[ToBoldlyGo]

Has the composition of the corks altered? Are they perhaps a little more, or less corky?

[MickYork]

Is how the scooter being used a factor.......more weight (it's an age thing !!), more long haul trips, less experienced riders, etc.

The oil may be a good call. With more "cleaning agents" being used does this effect the performance of the oil ? It would be good to see the spec' of the oil from 10 years ago compared to the modern oil being used. Obviously different manufacturers will have slightly different spec's.......or will they ?

[HxPaul]

How recent did you change the clutch plates...........Did you have the same problem with the old clutch plates........How recent did you change the oil..........Have you always used st90 oil?