Headstock Bearings

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Dec 26, 2007
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I am new to the forum. My Commando is #: 127703.

I am considering replacing the ball bearings & races in the headstock with the caged bearings (& spacer) from later Commando's.

Is this readily possible, or are there major pitfalls?
Stephen Chase

Thanks to all who sent advice.

The upshot seems to be:
a. add 6 mm to the spacer tube

b. press bearings into existing depressions in the headstock per normal re-assembly
Just knock out the races in the headstock and press in the new bearings and spacer. Easy as pie.
I seem to remember a prolonged discussion about machining a tube spacer to support the inter races. Dyno Dave was involved in that talk but I find nothing about it on his Atlantic Green technical Services web page.
There is a tube spacer P/N 0700100 which is a simple length of proper sized tubing to bear on the inner races when the crown is tightened. I don't have the measurements handy, but can get them if some one needs them.
I did this modification about a year ago on two early frames. I had to take the first frame to a machine shop to have the lower head-stock hole deepened to accomodate the later type yokes, otherwise the lower bearing does not fit far enough up into the frame to allow the spacer to touch the bearings, nor allow the yoke (triple clamp) spindle to fully engage all the threads. This was an expensive and time-consuming excercise which I first tried to do myself insitu but with no luck. I would only do this modification again if I had the bike dismantled fully for some other reason. The other bike used the standard earlier type yokes and I had to add a bit to the bearing spacer to get the correct preload.
Hmmm. Did this on a '70 S a few years ago and had no problem. With the sealed ball bearings there is no preload per se. The spacer provides the surface on which the inner races ride, so you want the bearings seated in the frame and the spacer should fit snugly between them. If the spacer is too short it can be shimmed or the indent in the frame deepened.
When I did this I found the standard spacer was short by about 6mm and rattled about until I made an additional spacer. The preload I was refering to is, as Ron L states, simply for the inner races to bear snugly against the spacer. It is a very difficult job to deepen the indent in the headstock, given that the bearing is a snug concentric fit in this bore.
I tried with hand-grinders, cutters etc. and finally had to take the frame to a machine shop.[/b]
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