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Old 09-29-2013, 02:56 AM   #1404
Box'a'bits OP
In need of repair
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Joined: Sep 2008
Location: Wellington, New Zealand
Oddometer: 2,393
Gearbox recon - part five

Notes on gearbox while I remember.

I didn’t disassemble the input shaft – I didn’t have anyway of relieving the spring pressure on the circlip. Maybe next time. As a result, I haven’t replaced the input shaft roller bearing & bush. The bush has some marks from the prior seal. The bearing has quite a bit less movement than the corresponding bearing that came out of the RS. Next time maybe.

The little input shaft pushrod seal is a truly trying little piece of German engineering. I needed to pull the input shaft output side bush off the shaft to allow me to punch this through & out of the back of the bush. Then I reassembled the seal into the bush from the rear, pushed it through to the front, & then pressed the bush back onto the shaft. The corresponding bearing got a nice new baffle on the input side, given I’d munted that getting the old bearing off.

The layshaft bearings were replaced. I used the bearing splitter on one as there was not clearance between the bearing & the nearest gear.

As much as I would have liked a lower 1st, I was too cheap to buy this & the shaft would have required a big press to remove & replace this. Likewise the higher fifth (though this was less attractive for me).

I heated the bearings in hot oil, & froze the shafts. I still needed to ‘persuade’ the bearings to go on.

I put a spring clip under the circlip, to allow for the radius in the input side output shaft bearing. Nice & tight. Hopefully won't move.

Parts diagram courtesy of Max BMW. I had to reassemble the output shaft twice. I put a washer in the wrong place, noted some slop on the middle gear (11 above). I realized my mistake, & had to pull the output side bearing again to correct this.

I haven't replaced the selector forks, or the bronze bush (14 above) that was showing some marking.

To reassemble the gearbox, the layshaft, output shaft, & one gear selector needed to be repositioned in the gearbox as one assembly. The other 2 selector forks could be installed after the event because the shaft they moved on was able to be removed. I had to push the layshaft & output shaft into the gearbox three times. The first time the shaft slid in fairly nicely, but I realized too late that I hadn’t put in the one selector on the immoveable shaft. Consequently I had to reheat the gearbox case end in order to release the gear shafts again. The second time the gearbox wasn’t hot enough (I was rushing), & the bearing hung up in the case. The third time I heated the box longer & hotter (150 degrees in Mandy’s oven – but the case was spotless your honor). Perfect. I'll add more photos tomorrow. And I'll start to look at the shimming.
My '91 R100GS thread is here
My Ride photos are here

It's just better when there's twins involved....

Box'a'bits screwed with this post 09-29-2013 at 03:13 AM
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