More Rebuild Questions - 160 Junior

[gregwils]

I hate to keep starting new threads with my questions, so I will create this thread and keep it going.

I put new bearings in the case and am noticing some slight clearance issues between the inner races and the shafts. For example, I installed a new 6024 bearing in the output shaft to the chain. The inner race of the bearing is listed as 20mm, but I am getting 19.83 with a micrometer. The shaft measures around 20.03. Is this common? I would rather feed the shaft with hand pressure and a slight bit of wiggle to walk it in, but its not going easily. Is this common? I know I can freeze the shaft and warm the bearing, but if I need to get it out, that could be a bit of a challenge.

Thoughts?

[Duccout]

I think that is normal, certainly the vee twins gearbox shafts can be very tight in the bearings and have to be tapped in with a plastic hammer. It helps as you fit the shafts into the bearing if you gently tap the inner race down the shaft with a punch.


Cheers,

Colin

[Ventodue]

So the difference between the OD of the shaft and the ID of the race is 0.2mm?

Hmmm. That sounds more than I would expect, even for an interference fit - an interference fit being what you're looking for in this application (outer race still, inner race rotating).

A quick review of bearing manufacturers' websites on Tinternet suggests the same (SKF, NSK, ano).

I might advise caution. But let the engineers speak ...

[Duccout]

Hi Craig,

Yes, I believe that the bearing measurements are absolutely accurate, ie a 20mm inner race should be exactly 20mm (give or take a micron) so the Ducati shaft should be smaller than this to allow an interference fit. They are usually very tight, but if the shaft were bigger than the bearing, it would not be possible for the two to fit together.

Cheers,

Colin

[gregwils]

Thanks guys. The great thing about doing your own work is if you have questions or concerns, you can stop and ask. Age does provide some degree of wisdom - stop and ask - compared to the trail of costly mistakes I made in days of yore.