Big end
should be fine, also the gearbox.
Big end can be checked when the topend comes off. I'd be very surprised if there was a problem.
A rebore is highly recommended (pay for it yourself if they are reluctant) assuming the cylinder is worn anywhere near the limit of the specs. In other words err on the side of caution.
If replacing the piston and rings anyway, the rebore is the
only additional cost to have as new, and it's only $50 or so to rebore.
Might as well have a look at the valves while it's apart, perhaps a light grind, and then you're as new.
TIP:
Pay especial attention to the bleed procedure when changing oil - MANY KTM's have blown big time because the procedure wasn't religiously adhered to.
Sounds like the shop is a good one, so work
with them in solving the problem. MAke sure they know where you're headed, and that you are prepared to pay extra if they suggest something more is needed
for your special requirements (long trip to Siberia!) that isn't covered by their warranty.
Good luck, and try and learn as much as you can by watching and talking to the mechanic - and be prepared to pay for that too! I've asked to watch and learn and offered to pay something extra for the lesson - well worthwhile.
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Grant Johnson
Seek, and ye shall find.
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One world, Two wheels.
www.HorizonsUnlimited.com