Bevel gear top bearing housing

[George]

Fitting a distance piece between bottom of recess and bearing outer will push housing up to far and interfere with bevel gears. If you are going to fit spacer it will have to be between top of housing lip and head. I would advise that you put bevel shims equal either side of bearing inner fit to head and check how far housing goes into head measure gap between housing lip and head and then make spacer to fit. I would not fit gasket it's just another unknown. You will then be able to set bevel gears without play. Just trying to make the best of a poor design.

[Jordan]

Not so sure about poor design, but getting shims in needed sizes can be a pain.

[ducwiz]

Fitting a distance piece between bottom of recess and bearing outer will push housing up to far and interfere with bevel gears. If you are going to fit spacer it will have to be between top of housing lip and head. I would advise that you put bevel shims equal either side of bearing inner fit to head and check how far housing goes into head measure gap between housing lip and head and then make spacer to fit. I would not fit gasket it's just another unknown. You will then be able to set bevel gears without play. Just trying to make the best of a poor design.

Remark: it's more than 20 ys ago that I had a 100/125/160 head on the bench. And unfortunately, there seems to be no cross sectional drawing of the upper bevel bearing details available in the workshop or user manuals. This made it difficult for me to think about the problem and give advice.
After all, then one has to make a distance ring (plane-parallel!) fitting between the lip of the bearing housing and it's seat in the head. Tghis will compensate the bearing housings looseness, putting it into a position where the correct shimming of the bevel gears can be done. In turn, the "tunnel" will press the bearing housing against the head and fix it against any movement, if a gasket of proper thickness is provided.

Hans

[George]

I am new to Ducati but will try to give my idea of how top bevel housing is assembled.
I believe that Mototrans are different assembly to Italian models.
Looking at my drawing it would seem that housing is held in place by light push fit in head with no positive stop to head. Thrust from bevel gear would tend to push bearing housing downwards. The bearing housing is prevented from turning by roll pin inserted into tube and fitted into slot in bearing housing lip. If there is any wear on head bore or bearing housing where it fits into head the housing can move about, accelerating wear. If bearing housing is a tight fit this would cause problems fitting and removing when setting bevel gears. this is the reason I am having a bearing housing made with a wider bottom lip to give a positive stop, that is, the bottom lip will be slightly wider than tube recess.
Of course there are over size bearing housings available but if head bore is worn oval the head would need machining or the problem would soon be back.
If anyone can see anything wrong with my take on this I welcome your views.

[Duccout]

What I don't understand is why Mototrans and made the housing this way? As an engineer friend of mine used to say to me: "They are not idiots who design these bikes!" I can only assume that the design was modified to make it cheaper to assemble. It amazes me that a country like Spain in the 1950's would agree to produce an engine like the Ducati bevel anyway, which in production terms is economic suicide; those bevel gears might appeal to race enthusiasts, but require skilled workers to assemble.