Join Date: Jan 2017
Location: San Antonio, TX
Well, replacing a seal without replacing the shaft will lead to more chewed seals if the shaft is at fault. That's why the dealer went straight to replacing the shaft, to cut down on potentially wasteful repairs.
An easier way to check if coolant is going into oil is monitoring the level of coolant in the overflow tank. If you see it going down (I did in my case), then coolant is getting pushed into the crankcase.
I am in US, and have no idea how much the warranty work was; to me, it was free. I should've bought the mechanics some beer or something, but my dealer is 1.5 hours away, so being grateful was not the first thing on my mind (Austin traffic was).
A used engine might not be safe from the badly manufactured balancer shaft; it more depends on the date of manufacturing. I think KTM updated the shaft at some point.