Putting a fat yoke in a thin head stock – bearings?

[G]

I want to put a larger yoke in to a smaller head stock. At the moment the main shaft (yes, I knew this was going to sound dodgy somehow!) doesn’t quite fit in, though the very top which is slightly narrower does.

If I get the shaft skimmed down to match the top, what’s the likelihood I’ll be able to find bearings that will still do an ok job?
Think the original (ball, not needle roller) bearing race stuck out a few mm as it was.

Sorry, no more details right now, will get some measurements and look on bearing sites tonight, but looking for any other general comments right now as taking the yoke to a CNC place at lunch time to see what they can do.

[tatters]

A CNC would,nt be any good, press out the stem and have someone with a lathe take it down to the diameter required of course leaving enought at the end to fit back in to the yoke with a flush fit.

With bearings find tapered needle bearings that OD fit the headstock with a ID that you can machine the stem down to.
____________________
Past:NRG50,AF1125(x2),NSR125RR,ZZR250,CX500,VFR400,KR1S,ZZR600(x2),CB400N,YZF1000(x2),KH125,Z200,FX400R,CBR954RR(x2)GPZ500S,GT550,VFR750F(x2),RD350N,XR650R,CBR600F,CB250,KDX250,YZF750R,CRM250,400EXC,KLR650,TTR600RE,DR350S,R100GSPD,RGV250,VMAX1200,DL650,KZ750 Present:G650XC,C12,CRF450X,1190ADV

[G]

I’m taking it to a bike-specific machine shop that should be able to do what’s needed (whether they need to press it out or not to stick it on a lathe). Sorry, just generically used ‘CNC’ - they may or may not use a CNC lathe in this case .
I’d much prefer to use needle roller bearings, but not sure there’ll be space for the right type – while presumably may be able to get ball bearings in a bit narrower configuration?

[MarJay]

[G]

Hopefully – it’s pretech I’m taking it to this lunch time .
As it’s a pretty simple job, I don’t see the problem with that – it’s with getting bearings to fit. It would be much easier for me if I could get it to fit without skimming it down more than the top section – that way I wouldn’t need to make a shim for the top yoke or other general hassle like the threaded section for the top yolk nut being too thin (though could possibly stick a threaded rod through it instead).

[G]

Took it to pretech and they reckon it should be ok without pressing it out.
However I think finding bearings is still going to be an issue – seems I need a total of at least 12mm clearance on the radius, which I suspect I won’t have (minimum OD 24mm bigger than ID in the size I’m looking at, from what I can see on a couple of sites). If anything, ball bearings look to be worse not better than roller ones.

[G]

The cup for the bearings seems to be 40.5mm.
The inner diameter of the headstock is around 28mm.
The top of the yoke shaft where the upper yolk clamps is 27.8mm or there abouts, the rest is 28.5mm.

Outside of bearings made for steering, very little comes close to these sizes. A few thrust bearings, maybe.

Wemoto offer a 41mm * 24mm taper roller headrace bearing. 2mm off all around should be fine considering the bike will probably have 1/10th the power the yokes were designed for.

I could also consider push bike headset bearings. A lot of these seem to be 41mm OD - however it seems they are actually too thin for my needs, as this matches up to 1 1/8" ID, which is about the right size now, but unfortunately too big for the headstock.
I've looked at the headstock and don't really want to take any metal away from it.

Any other suggestions? While writing this out and reading what I wrote, it seems getting it skimmed for the 41mm * 24mm is the only sensible path really.

[Pete.]

Better to find the bearings, then machine parts to fit.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good