Numpty Question

Is there a reason why there is a spring in the slave cylinder, and does it have to be that strong - this applies to the 25mm piston.

I assume that it is there to provide continuous pressure on the pushrod and release bearing??

Thanks

Probably just there to take up slack and reduce free play.
If your clutch is too heavy
Paul Brice had good results with new radial master cylinders (clutch pump).
As you know i fitted a modified Oberon command (slave) cylinder which i am very happy with

I recently emailed Oberon about one for the Guzzi, mentioning I had seen your conversion, they replied back that due to the amount of modification the slave cylinder would require a new CNC programme and need new jaws. They didn't believe it was viable to produce this for the estimated demand.

Still thinking about getting the CLU1200 and getting it machined.

BrianD wrote:

I recently emailed Oberon about one for the Guzzi, mentioning I had seen your conversion, they replied back that due to the amount of modification the slave cylinder would require a new CNC programme and need new jaws.  They didn't believe it was viable to produce this for the estimated demand.

That is annoying - although they are probably right

Another fix is a later clutch assembly - there has been a thread about this - so if your clutch is worn - or you have another reason to completely unassemble your Guzzi??  That may not be too expensive

I was having a look around to see how much a second-hand Aprilia unit would be, and also searched for Moto Guzzi ones. Some of the MG one have a large piston whereas my spare has a 25mm piston (unless its an optical illusion).

Can anyone comment on the differing piston sizes [Looks though machining would be required - so maybe different gearbox], but would this account for the amount of effort if you have the small piston?

25mm is standard on the GRiSO.
The larger the slave or as Guzzi say "command" piston, the lighter the clutch will be.  This is because the clutch pump (master cylinder) displaces a fixed volume of fluid. A larger command piston has to move less to accept that fluid and therefore compresses the spring less. So that is less work at the hand lever

When the piston extends it  goes into a 26mm (ish) hole in the gearbox end case that holds the thrust body, that drives the pushrod. So any piston with a diameter above 25mm needs to be reduced at the end or it stops short as it hits the gearbox end case. I found that out by experience.