This is less of a problem then a technical discussion of the modifications carried by the factory out over the manufacturing life of the motor to the clutch cluster.  If your 650/668 is prior to engine number 1461 then this probably applies to your bike.

Technical Bulletin 04/99

Upgrading to the clutch cluster

"Herewith following, you find the chronological description, from the early 650 c.c. models up to the current production, of the various improvements to the clutch systems of our engines. The purpose of this bulletin is to resume in a single technical document all modifications carried out on the clutch.  Please refer to spare parts catalogue 650 and 750 for the engine nos. involved in these changes.

Clutch Bell

"Due to the use of 9 disks instead of the previous 8, the space between the end of the petals and the abutting end of the ring gear of the primary transmission has been varied from 45,6 up to 50 mm.; nickleplating (please see the herewith attached drawing 1)." [Sorry, don't have this one - Steve].

"Please be also informed that, due to a machining mistake of the original Manufacturer, on several clutch bells it has been performed the following modification.  The early clutch bells (part number 046005000039) had the ring gear reduced down to 26 mm (rather than 26,5 mm).  To provide for this inconvenient, it has been necessary to modify the internal ring of the cage of the INA needle journal, reducing it from 26,5 mm (part number 022008000024) down to 26 mm (part number 022008000026).  It has also been necessary to adopt a 3,3 mm. shimmer (part number 033001000023) between the ring gear and the fixing nut in place of the standard 2,65 mm. unit (part number 033001000069).

"Once the stock of above-mentioned bells has been over, their part number has been varied from 046005000039 to 046005000045 (attachment no 4). [Sorry, don't have that either - Steve].


"Varied the dimension indicated in the herewith attached drawing 2/B from 31,5 up to 35,6 mm., along with the passage from 8 up to 9 lined disks.

"Modification of the dimension between the end of the hub with slotted profile and external surface, from 20,5 up to 19,2 mm (please see attachment 2/A); (this modification doe snot imply a modification to the nearby component parts).

Spring carrying disk

"Varied the sealing of the journal for the usage of the thrust bearing aand varied some dimensions as indicated (please see the attachment 3/A-B-C-D).

Lined disk

"For the latest specification, it has been reduced from 3 down to 2,7 mm., along with the passage from 8 up to 9 disks.

Steel disk

"The thickness of the steel disk has been increased from 1,2 up to 1,5 mm., along with the passage from 7 up to 8 disks.

"PLEASE NOTE: The motorcycles in current production are fitted with 9 lined disks having the thickness of 2,7 mm and no 8 1,5mm steel disks.

Clutch spring

"The specific features of the spring have been modified and the motorcycles of current production (having 9 lined and 8 steel disks) the total coils are 7,7 including the flat ones and the initial length is of 37,5 mm.  The thickness of the wire is 2,8 mm. and the external diameter is 21 mm.

Clutch Cluster Technical Bulletin

© Steve Carr, 2001-2007

Site created February, 2000.  Last modified Friday, May 15, 2009

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Last updated
30 May 2005