Yamaha R1 gearbox troubles

I’ve just bought a 2004 Yamaha R1. It shifts through all the gears fine if going steady but if I am accelerating hard when I shift into fifth it will hit a false neutral then find sixth. I’m thinking it’s the selector forks bent or worn dogs? I’ve also heard there is a return spring that could possibly be causing the problem. Any idea how much I should expect for a garage to remove the engine and rebuild the gearbox?
Durham4416, MCN forums
 
We’d guess that the fifth gear engagement dogs are worn… Third is the gear that’s slid across for engagement, sixth is the other side of third. So if fifth engagement gets spat out hard enough it’ll send third across into sixth… (still with us?). There are lots of bit inside the engine that shouldn’t allow that to happen, not to mention a size nine boot on the shift lever, but that’s what we’d be looking for/at.

The engine will need stripping and the above gears inspected. Plus the selector fork on third and the selector drum. You should also take a look at the mating gears for the above to ensure no damage has been done when it’s jumped out of gear, plus the selector detent roller and spring.

Cost-wise it’s got to be the best part of a couple of days work to change agear. Gears and gaskets aren’t cheap either with gears ranging between £70-£130ish.