... and the 3rd one...

[Chris in Japan]

And the third one, guys...

In any gear, when gear box under high load, the gear slips. I slightly reduce throttle and does not slip any more. Any kind of noise is gear - just that feeling that the gear box disengages for a fraction of second.

I guess you will tell me that those parts that shift axially in the box and engage the gears in the shaft are worn out, rounded, and this is the reason for, but having exactly the same problem in all gears, this sound anyway strange to me.

Maybe important: I have a gear box oil (I believe 90W) in there and not a 15W40. Other thing: I filled the gear box with the bike on the side stand, maybe over-filling it...

Any help is welcomed!

[Chris Haynes]

90wt is too thick and won't properly lubricate. That is unless it is an EP90 that has the viscosity of 30wt.
Gears and gear dogs don't slip. Sounds like another clutch problem.

[Chris in Japan]

Indeed, Chris!

Emptied the wrong 90W, refilled with 750ml of 15W40 and problem solved!

Many thanks for the effective advice!

Regarding the dogs, I was convinced that wear on them and/or wear in the cavities of the main gears where they engage could cause the dogs to be "expelled" out and cause that "slipping" in the gear box...

However it is, it is not happening anymore! Great!