i have a good bit of knowledge now of them. they handle well, the suspension is excellent, in TBM three years ago it was the first bike to win a test v the ktm450 whixh had won for 3 years.
they eat wheel bearings in our climate and bottom suspension needle roller. poor seals. plastics are only ok and the speedo packs up before you getit home virtually!
they have locknut and screw tappets and generally a really nice bike.
so as i say, plastics ify, bearings and seals poor, electrics poor, ride fantastic (the best) handling very good, power about the same. the 520 beta is considered the business!
250 was gutless in the midrange.
regards
Taffy