Steering head bearings

[bsaketcase650]

Hi,

Can anyone tell me if there are differences in the sizes of the bearing races between those fitted to swing arm models and those to plunger frames models. My problem is as follows:

I am now in the reassembly stage of my plunger framed 1953 A7 Star Twin. As part of the rebuild I removed the old cup and cones as they were clearly worn. I ordered a new set of cup and cones together with ball bearings from a well known supplier.( I noticed that whilst they appeared similar to the originals they did not have the fine threading on their inner edges which I understand are used when using the appropriate tool to drive them out).
 The new cups were fully driven into the steering heads and the bottom cone fitted to the lower yoke steering stem. I greased up the cups, put in the bearings and fitted the bottom and top yokes. I  tightened the steering stem adjuster sleeve until the bearings moved smoothly without any play or binding.
I have then trial fitted the fork leg shrouds and the diver helmet cowel and have found that the bolt holes on the cowel which should engage with the lower yoke pinch bolts now sit approximately 1/4" above the the lower yoke bolt holes and the fork shrouds about the same distance below the upper yoke.
On closer examination it seems to me that the lower and upper cones sit too proud of the lower and upper edges of the steering head. I am now wondering if the depth of the cups are different between s/a and plunger models which is now in effect causing the upper and lower yolks to be too far apart and hence the misalignment at the points that the tinware should fit to the yokes.
Any ideas or advice?
Thanks,

Simon

[muskrat]

G'day Simon,
                  part #'s are the same in my books, 65-5126, 66-4149 x 2, 65-5127. Might have to push one back out to compare against an old one. While it's out measure the depth to the shoulder in the headstock and the cup to work out how deep it must go.
Cheers.

[bsaketcase650]

Attached is a photo showing the top bearing cup - the cup is fully driven home into the shoulder of the steering head but seems to be sitting too high. What do you think? Is this correct or am I missing something here!

Regards,

Simon

[iansoady]

Looks much too high to me. It should bottom out on the annulus inside the headstock - you can usually hear this when you drive it in as the note will go from a dullish thud to a ringing sound.

[trevinoz]

Simon,
              The obvious question is, how do the new cups compare to the old?
    Trev.

[bsaketcase650]

Trev,

Wish I could answer that. Like the plonker I obviously am, I chucked the old bearings before fitting the current ones!! Lesson learnt - keep everything, even if the original item appears to be fit only for scrap.

Simon

[te_52A7]

Hi Guys, I had a similar, but opposite event when I replaced the balls with a roller bearing. The outer race was sitting to low in the neck and the rollers were actually touching the neck frame when inserted. Wasn't expecting that. Had to make up a shim to raise the outer race enough to give the rollers some clearance. It didn't appear that the neck had been altered in anyway and the original bearings (with the thread) fitted fine. This was the same on top & bottom. I too bought these from reputable UK dealer and assumed that they would be the same dimensions as the originals.......thats what ya get

[Stu55Flash]

From memory when I did mine there is about 1mm of flange below the bearing raceway on the cup and about 2mm above. It looks like there is too much material on your cup.

Stu

[Brian]

I think the problem is with the races themselves. An original BSA cup is 1/2" high. The problem with the ones you have and most new ones available now is the balls sit too high in the cup. If you look at the ones you have you can see the ground section where the balls sit is about half way up the cup, in the originals the balls sit quite low in the cup.

What this means is when you measure the cups and cones in their individual pieces they will all measure the same but when the races are assembled there will be quite a difference in height between the originals and the repro ones.