Early Super Rat Rear Hub Question

[DesertRat54]

I'm re-visiting the parts manuals for the M93, M93A, M93B and the B+ as I put together the final parts list for my M93A restoration. I noticed something that I'd not seen before, and am a bit puzzled by it. As all of you (or most of you ) probably know, the rear hub ("drive flange," #929285) is common to the 93A, the 93B, and the B+. Yet both the 93A and the 93B also feature a "rear sprocket spacer" (#939245). Why? The B+ doesn't use this piece, and in all other ways, the B+ rear wheel assembly is the same as those for both the 93A and the 93B. I want to build a "correct" M93A, and will purchase the spacer if that's what the manual calls for. Still, I don't get it unless it's a sort of reinforcement for the sprocket mounting holes.
Thanks,
Bill in VA

[taber hodaka]

The 93 had a offset sprocket and it was very weak. When sprockets fail, chains derail and can wipe out the shift cover. The sprocket was replaced with a flat sprocket with spacer. -----------Clarence

[DesertRat54]

Thanks, Clarence. I understand a bit more now in light of the dished rear sprocket that I know was used on the model 93. I'm still missing something, though--why doesn't the B+ also use the spacer? Isn't alignment between drive sprocket and rear sprocket still important enough to use the spacer on the B+? Or am I missing something? And a related question: Why not just use the stock B+ rear wheel (i.e. without the spacer) on an early Super Rat? Jeez, I hope I'm not being too anal-retentive about this...
Cheers,
Bill in VA

[taber hodaka]

The B or B+ also has the cushion hub. That is the way to go if you are not doing a restoration. The B and B+ with the cush hub sticks out further therefor you do not need the spacer.-------Clarence

[DesertRat54]

Ah yes, that makes sense. Thanks, Clarence.
Bill in VA

[squid on a 300]

I have an early 93 with a non cushioned hub I'll be restoring....are the spokes any different between the cushioned and non-cushioned hubs?
bob

[dirty_rat]

Yes, the spokes are longer on the non-cushioned hub. If you look at the two hubs, the cushioned one is larger diameter (and has larger diameter brakes and a larger diameter axle). The swingarms are also different. The non-cushioned hub bikes had a smaller rear axle and therefore the axle cutout in the swingarm is smaller ( 12mm compared to 15mm in the cushioned hub bikes). So, if you want to upgrade from a non-cushioned hub to a cushioned hub, you also have to upgrade the swingarm to a newer one, or do surgery on the old one.