OP, from your description I would say the "dogs" on the 2nd and 3rd gear are worn and they will require replacement. I had this same thing happen to a built-up 120 TC at about 45K on the clock. I replaced mainshaft 2nd, 3rd and shift forks. Should be covered under warranty.

The dogs in the pic below are the protruding pieces on top of the gear. They get rounded off and causes the slipping. These dogs engage the mating gear. If they are worn, slippage can happen.

I'm curious if the fluid level is reading low/none. That is also a common issue transferring to the primary.

 

So there is no center nut and hex head that adjusts the clutch plates for wear?

I have not had my 18 limited apart and have only messed with the cable clutch bikes.

 

Nothing, nadda, zero, zip, nyet.

 

Interesting.

So even less to do during a service...

 

Exactly, and I'm sure they charge as much as ever, lol.

 

probably more because "this sucker bought a 30k dollar motorcycle, lets soak him for a bit more"...

Just another reason I do all my own service.

 

Absolutely NOT true.

 

My first guess, also.

 

While Vdeuce's answer is a prime candidate, I would also look at a couple of things. It's possible that the shift linkage is binding up in someway that the bike is not going all the way into gear. Under load it pops out. Also if the shift detent has a weak spring or is warn it won't go all the way into gear. It may also be something as bad as the tops of a few gear teeth are gone due to poor heat treat. You'd likely hear the some noise in that gear tho. I'd definitely drain the tranny oil and look for pieces, Could be gear clutch dogs or parts of gears in there.

 

Popping out of gear and landing in real neutral or a false neutral is easy to describe. Pops out of gear and rpms slam the rev limiter if you were on it. It's a connect / disconnect type of issue. In the game or not. No inbetween unless you are in between gears.... REALLY?