Hello everyone, it's time to call upon the master-mind of the Tenere community again



I was coming home from my brief European voyage last weekend and at some point, I had to take the highway as I was someone rushed. Got on the highway rode at ~130km/h for some time, then decided to change the tempo a little and bumped it up to ~140. I was happily cruising along for a short while, when suddenly the bike jerked pretty hard and then continued on as if nothing has happened.


At first, I haven't even realized what has transpired: it felt as if the brakes came on hard very briefly and then released just as suddenly. I slowed down considerably, tested the brakes - they seemed to be working fine. Stopped the bike, got off and inspected the disks and the calipers - everything looked just like it should have to my untrained eye.



Got back onto the bike and started riding, doing 120-130km/h for a while to see if the issue manifests again. It didn't, so I decided to try 140-145. In just under 5 minutes, I got the same "surprise", although it wasn't a surprise anymore as I was watching for it.



What happens is that the gearbox shifts from 5th gear down to the 4th gear and then back to the 5th gear very quickly, all by itself. Upon shifting down, the bike immediately starts to engine-brake, and then accelerates when it shifts back up to fifth, causing this sudden jerk I did not appreciate that much.



I slowed down a little, to ~130-135 km/h to see if this changes anything and it did - the bike would not shift gears without my input and I went on riding well into the night that day.



The next day, I completely forgot about the ordeal and at some point, I ran into the problem again, only this time, slowing down to ~135 did not help that much, it would still do these uncalled for gear shifts, I had to slow down to about ~125 before it stopped doing that. At that point, I stopped experimenting, since I still had to do over 1000km to get home and getting stuck this far from familiar mechanics and tools wasn't something I had the time for.



Now, exceeding "critical" speed when overtaking cars was totally fine - I could accelerate up to ~150 when I needed to pass someone, it seemed as if only steady riding at certain speed would cause these gearing problems.



At this stage, I don't have that many ideas of what may be causing such behavior. The only thing I have noticed "abnormal" is that oil level has started dropping somewhat towards the end of the trip and I did not have any I could top it up with. In the beginning of this ~5000km trip my oil level was reaching approximately 1/3 of the way up the dipstick and it was closer to the E mark towards the end of the trip. However, this may be normal oil consumption for "high speed" riding.


Any ideas,, feedback and suggestions will be highly appreciated. I don't usually ride at that speed while at home, since there is no reason for me to do so, but would like to get this sorted out before I undertake my next extended trip. Thanks!

In my experience when a gear jumps it's caused by the "dogs" on the gear (the three prong like bits sticking out the side of the gear not the gear teeth) being worn. This causes the gears to slip back down the box. You can dress the faces of the dogs to stop it happening but that is a bit of a bodge as gears are case hardened.

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That's one of the things that came to mind at first, however if the dogs were worn, wouldn't the bike just shift down a gear and stay there, as opposed to immediately shifting back to the fifth gear?

what came down my mind wat the spring of the gear lever (inside the cases) that might not keep the lever mechanism where it should stay.
open the cases whenever you can. i'd be very weiry riding that engine like that, and at those speeds...
fact that you can still ride it, makes it not that dramatically, but it might any time soon!
oil consumption is due to highway speeds over 5000rpm... we all have it.

hannesd makes a good point. I changed my stopper arm and spring as a preventative measure relating to it being a potential cause for a failing 3rd gear. This had been mentioned a few times on this forum as a 'suspect' part, sometimes blaming the bearing on the stopper arm and sometimes mentioning a weak spring.

It took about 90 minutes to fit .

Stopper arm is part 11
Spring is part 9

https://www.ajsutton.co.uk/genuinepa...ear-drum?uID=0

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Thanks, guys, this does sound reasonable. I will talk about this with my mechanic and then decide on the best course of action. I may continue commuting and riding the bike on dirt/gravel roads around my home town to see if the issue manifests itself in these conditions - I am not too concerned about gearbox failure this close to home as organizing a "rescue mission" is much easier and cheaper here. I will definitely take the gearbox apart for inspection before I undertake another lengthy trip.



BTW, I did an oil change this past weekend and it looks like ~400ml of oil were consumed on this ~5000km trip. The oil filter seemed fine - no dust, no metal shavings, just used darkened oil on it.