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When shimming the upper bevel gear (narrow case 250 but I don't think that matters) do shims go both above and below the bearing or just on one side of the bearing? The parts book shows shims above the bearing. The Clymer manual appears to show two different things: the assembly drawing on page 29 shows shims above and below, the drawing on p. 87 looks like the shims are below the bearing (although there is a hint of a shim above the bearing too).
If the shims are only above the bearing I don't see the purpose of the Seeger (snap) ring below the bearing so I suspect that shims go on both sides. My bike has always had shims on both sides but since it's been through several owners I'd like to confirm if this is correct.
Let me know.
Thanks,
Phil

The vertical bevel shaft that has the gear on top would need to be finely positioned to mesh correctly with the gear on the camshaft.
That might explain variations in manuals?

Shims are usually on both sides to get the mesh depth correct plus the total number of shims need to only just allow the circlip room to fit, do that first then adjust mesh. What fun!

Info about the shimming job: http://renato2.bplaced.net/DUCATI/dioc40_12-14.pdf

The procedure for the upper gears is the same as for the lower pair. In addition, you must put a special centering bush between the bevel shaft and it's cladding tube.

cheers Hans

The top shim should be selected first for a proper gear mesh to the cam gear, then if needed, add the lower shim to have zero play axially on the shaft. Also make sure that the bearing outer race is locked in place, e.g. if the gasket is too thick then the assembled bearing is not locked in the housing leading to major issue down the road.

Regards,
Brian

ducwiz wrote: In addition, you must put a special centering bush between the bevel shaft and it's cladding tube.

cheers Hans

and don't forget the snap ring above the said center bush to lock it in place.

Regards,
Brian

New circlips every time.