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Jean wrote:MS, If the number of teeth is not TOO different, the teeth can be made taller with a slightly fatter root and you can get away with changing the tooth count. I'd look hard at some sort of heavy-duty additive for this gearbox as the pitting suggests either it sat a long time and some of the teeth got rusty, or the oil wasn't as good as it should have been or maybe not filled properly.
PS to ME109. Running 5th gear without being at high speed and RPM can eat up gears pretty fast. What RPM are you currently running at 160KPH?

6000 rpm for 160 hph Jean.
I don't think my tranny has ever sat still, oil has always been changed yearly with good brand 80/90
I was thinking more like a end float/meshing issue? The tranny has shown no sign of 'bits' at all for 13 years.
Until now. Anyway it doesn't look bad in there at all, no damage that I can see to any other gears.
The pitting must have occurred in the last 12 months. I'm thinking a combination of bearing wear and gear wear.

Bearing wear can produce the same effect. But it looked like pitting was confined to only a few teeth and that was the basis for my observation.

Jean wrote:Bearing wear can produce the same effect. But it looked like pitting was confined to only a few teeth and that was the basis for my observation.

It's a bit of a strange one Jean, I couldn't understand how the gear could be worn on one side and not the other.
Other than being out of round.

Every revolution there is a power pulse at the same place on that gear, it may be something to think about. Eventually they get pitted all the way around. The mating gear seems to wear more evenly, possibly because the pitted teeth are mating at a different place each revolution. Another possibility is that I may be full of bullshit.

ME 109 wrote:[

6000 rpm for 160 hph Jean.

160 horses! Wow, I knew that RS was quick but...

I've got a taller 5th I'm going to put in (pre-X) and bought it from motobins. There is a bit of hearsay that comes up every time it is mentioned on advrider about taller 5th's. There are different suppliers and different hardening methods- I can't remember what or who but a quick search there should reveal it.
The thin is I've never read anyone actually reporting an issue with the lesser preferred ones I have.. To me it just seems like one of those internet things, oft repeated. I've talked to a couple of people who have used these gears in many gearbox builds for other people and they had no preference.

Looks like your making good progress Jeff.

robert wrote: Another possibility is that I may be full of bullshit.

We should get on alright then, Robert.

My G/S box was rebuilt for the PO by his local BMW guru with a low first and higher fifth - cost him over $2,500-!

But as I previously posted, there was something drastically wrong with the overall length of the output shaft assembly, with the new first gear too far south, to the point that it touched the outer race of the bearing on the adjacent shaft.

I finally managed to locate and replace all the spacers, circlips and a new shaft, but if anything this made things worse, and the only solution has been to reduce the thickness of the aftermarket low first gear by 15 thou.

This might be an isolated incident, and in any event it would have been picked up by anyone rebuilding the box if it had re-shimmed , but if you are doing the rebuild yourself it is probably worth while taking a bit time to check that any new gears are the same thickness as the ones they replace.
No sign of wear on the teeth, but I was using M1 full synth gear oil.

I am currently running a spare box with stock ratios, and I cant say I notice the difference from the ratios in modified box.

The gears on my B44 were pitted on the contact faces. I was advised by Modak in Melbourne, my nearest BSA expert,that this was because BSA initially recommended engine oil for the box, it wasn't up to the job, and I should use a good GL5 gear oil. Modak were able to replace the gears from their cache of ex Oz Army stock, and there have been no problems so far.

Thanks for the input Hans and Roy.

Might pay to just go with the stock ratios.

It's times when riding from Wentworth to Broken Hill and the likes, that the taller 5th is appealing.

I'm definitely pro the taller 5th- I'd like one on the R90 and with the G/S final drive and 1000cc's I think I'll need one and wish for more.
My 5th is mostly used for an overdrive gear anyway. If I start requiring serious work from it up twisty hills for example, I usually prefer to downshift and run higher rpms in 4th.
But then my R90, for whatever reason I don't know yet, seems to get its power pretty low and tends to run out of steam too high up. I like it just fine like that and have no desire to run mine up to 8K rpm like supershaft but running up slightly naughty highway speeds, I see the higher 5th as a pretty good thing.

No problems with that, I was just really bragging that my G/S is so smooth that I dont notice a few extra revs ----.