If it is a KTM they use a mineral oil. You can use ATF or fork oil. I have tried both and found fork oil to work best. Some other brands use brake fluid, DO NOT use it in a KTM, if it uses brake fluid it will say on the master cyl cap.
Wolf -- first of all "mineral oil" in European terminology is NOT the same as USA. It means mineral-based hydraulic oil, not the stuff you get at the drugstore. Fork oil is hydraulic oil, so is ATF, or you can get the type (AW 32 I think it's called?) that they use in tractors. You can get Magura hydraulic oil from KTM, but it is VERY expensive. I've used 2-wt fork oil, and liked it the best, but recently my master cylinder started to leak. Replaced the plunger assembly, now up to 10-wt fork oil, but it's still leaking. Ugh. Hope the mster cylinder isn't scored. And by the way, speaking of scored master cylinders, you've probably learned by now to avoid the Enduro Engineering (and other brands) of easy-pull clutch levers. They have a near-100% failure rate and can permanently damage the master cylinder. I love Enduro Engineering stuff, but any type of easy-pull lever puts the wrong angle of attack on the plunger.
SlowJ, I talked to the guy I bought the bike from and he used mineral oil bought at Walmart. He also said Baby oil minus fragrance =mineral oil.
It just doesn't sound right. I'll go with your suggestions as soon as I find time.
I have used Maxima rear shock fluid. Think it's 5 wt , any how its purple. My berger has had zero clutch probs. I've bled it average 4 month intervals. Back bleed with a big syringe it's messy but quick and easy.