Portugese layshaft bearing
- Thread starter lazyeye6
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Does anyone know when the Portugal brass cage bearing was first installed by the factory?
It seems like these are only found in 70 and up bikes.
Prior to that, a steel cage bearing was used?
It seems like these are only found in 70 and up bikes.
Prior to that, a steel cage bearing was used?
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The Portuguese bearing has been found in 850 Mk2/2A gearboxes (and all Mk3s) so from approximately the second half of 1973.
I can't remember any reports of Portuguese or other brass cage layshaft bearings having been found prior to the 850 Mk2/Mk2A unless anyone knows differently.
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I seem to remember seeing reports of failed layshaft bearings on 750 bikes as well. Don't know if they were brass or steel.
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Fit the 6203TB bearing per Mick Hemmings' advice and no shimming necessary.
Fitting a roller bearing loses the positive layshaft location, and as I found out, shimming isn't always 'fit and forget' due to the lack of dedicated thrust faces where the shims are fitted.
Mine loosened off over time, and I gave up on layshaft roller bearings after that.
To answer the question: Isolastic shims will fit at the kickstart end of the layshaft, once the inner diameter has been increased slightly.
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Oh man ,decisions, decisions
. By loosening off do you mean axially? If I ensured that the roller bearing race is bottomed out fully I would have thought the clearance would stay the same. Of course there is probably variation in the gasket material between the housings used perhaps by a few thou, but that would also be relevant even with a ball race as if the gasket was too thin would start to load the ball bearing race up to. Assuming that with the cover bolted up with either type of race would still be looking for a tiny bit of clearance?
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Oh man ,decisions, decisions
You can measure the end float without stripping the gearbox by measuring between the kickstart lever and the case (or a dial gauge can be used on the end of the kickstart shaft again without having to strip the gearbox).
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The kickstart to outer housing clearance was giving me approx .020” with feeler gauges. I continued to investigate further and found some shims inside the inner cover 
. After removing the layshaft I found a needle roller bearing, so the decision has already been made for me. Will validate that clearance dimension later on as it appears to be too large. BTW the box shifted quite nicely and into neutral easily etc, I did not have a complaint about that side of it
. After removing the layshaft I found a needle roller bearing, so the decision has already been made for me. Will validate that clearance dimension later on as it appears to be too large. BTW the box shifted quite nicely and into neutral easily etc, I did not have a complaint about that side of it
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I take it that is the end play measurement not just the gap between the kickstart and the cover?
Hopefully, an NJ203E roller (not exactly a needle roller) bearing?
0.020" isn't excessive.
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Yes end play. Roller bearing, FAG manufacture although the writing on it is facing into the blind housing I can see the writing on the inner race located on the layshaft. I saw somewhere to aim for .005”,I’ll try and obtain that.
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Something that confuses me is that Hemmings talks about the layshaft being a sliding fit in the bearing. Even mentions easing the fit if it's tight. Doesn't that obviate the location benefit of the ball bearing?
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Back in the day I replaced many of these bearings before they cratered and a good many more afterward. The good news for owners was that this could be done without removing the gearbox or dismantling the primary drive, PROVIDING that the shell hadn't cracked or worse. We often found hairline cracks between the layshaft and mainshaft bearing bores even on gearboxes just in for overhaul that had not suffered a catastrophic bearing failure.
When the layshaft bearing fails you're very lucky if it doesn't ruin the shell, aside from the possibility of a wreck when the wheel locks up. It happened to me once when just pulling off from a stop sign before entering the freeway on ramp. My lucky day. Also my friend with the pickup truck was home watching football that day and it was a short walk to the pay-phone booth, and I had a quarter in my pocket.
When the layshaft bearing fails you're very lucky if it doesn't ruin the shell, aside from the possibility of a wreck when the wheel locks up. It happened to me once when just pulling off from a stop sign before entering the freeway on ramp. My lucky day. Also my friend with the pickup truck was home watching football that day and it was a short walk to the pay-phone booth, and I had a quarter in my pocket.
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