When the valves went on the KTM 400RFS engine in my Beta I took it to Bill at 5th gear in Richmond and he replaced them with Kibblewhite stainless steel valves - much more durable than the OEM titanium valves. The head needed to be re-machined and, if I remember correctly, he had Wally Routledge in Langley do the machining. I was very satisfied with the end result.
John