I may be interested.

Your 250 was originally designed as a 250, and therefore has some reliability.

The big KTM's are derived from the 450, (the 525 is a big bore version), and the 560 is a bored and stroked race bike. The stress on the engine components and cases far exceeds those that it was originally designed for, now that it makes around 65% more power than originally planned.
As a consequence, KTM state seemingly ridiculous, but ultimately necessary service intervals.

It's a 75hp race bike with a bottom end, and drivetrain no stronger than a 250.
Infact, the six speed ktm's have really narrow 5th and 6th gear cogs, and they bust gearboxes with a 450 lump on the end of them.
Add in the fact that it has no balance shaft, and you've got a huge lump of ovalised bearings, and engine schrapnel sitting underneath you in no time at all.

A 400 EXC is probably the pick of the bunch if you want a four stroke KTM for stunting.

cant rule out KTMs Lc4 motor for stunting reliable but LC4's are a bit heavy, i know mine is pretty heavy, but its just about bullet proof. and they run about the same hp as a new 450 a stock 450 at that, but i mean theres mods you can get, but the more you build up the less reliable it gets. But i like it, i cant complain. But Goodluckmonkey is right about the 560 and 525.

MINE TOO...

sold...no questions asked..ill pm you my number