[Mastermind]

Hello all,

I had a very concerning issue on my way back from work today.
When entering the highway I shifted from 3rd to 4th gear to merge in the traffic when my bike downshifted from 4th to 3rd with a big hicup.

From then I was unable to stay in 4th gear. I soon as I turn the throttle the bike goes back to 3rd gear. 5th and 6th gears work fine tough.

I noticed during my last two rides that the gearbox was a lot less smooth than it used to be, but I didn't pay attention since it had recently been serviced and sometime the shifter calibration may be reset.

Now I'm afraid my gearbox might be beyonbd repaired and needs a replacement, witch is unfortunate as it is no more under guarantee and last scheduled service was not done by BMW (but in time and correctly).

Have you ever heard of such behavior ? do you have any clue what part may be responsible of the failure ?

In the case I have to replace the gearbox, are you aware of any tutorial ?

Thank you guys for your help.

The bike : 2015 R1200R LC with 33 000 km.

 

[r0ckrat]

Questions just to remove a few possible issues...

1) Are you shifting using ShiftAssitPro, and at what RPM?
2) At what RPM does it drop out of 4th when attempting to accelerate?
3) Have you tried running up fairly high in the RPM range, shifting manually from 3 to 4, and then accelerating further in 4th?

One other thing to try would be to go from 3 to 5 then down to 4, and see if it holds.

I have no idea what might be the problem, but a possibility is a bent 4th gear shift fork, which then doesn't fully engage 4th allowing it to pop back out. (This was a not uncommon issue in the Suzuki SV650 world with 2nd gear.)

 

[mjgt]

I had a similar thing happen to me with my Honda CB 550 F2, I think it was 4th but it could have been 3rd. Anyway when I took the engine out and stripped it down I found it was the three dogs on the side of the gear had sheared off. Replaced the cog and rebuilt the engine, bike worked fine for the next 8 years when I sold it. If that's what has happened you should be able to fix it up.

 

[Panzermann]

As indicated by other posters, such behaviour is normally associated with either a bent selector fork or worn dogs on the gears. Neither is in any way typical for a Roadster of your mileage. The only other causes of shifting problems I have experienced on a bike have been:

• when a countershaft output bearing on my Suzuki T500 collapsed and some of the bearing cage got caught in the selector drum cam grooves, and
• binding gear lever shaft (although that normally affects more than one gear).

If it's internal, then unfortunately you're likely to suffer significant hurt to the hip pocket. Parts aren't cheap and you won't know what is needed until it is disassembled – labour costs will be very high just to get the gearbox out and opened up. I don't know about the availability of good used gearboxes.

My vague recollection is that the BMW manual doesn't cover gearbox refurbishment, and neither does the Haynes.