im actually running a non "o"ring KTM chain on my 300 which was a simple act of foolishness by me. I asked for a chain for the 300 and I didn't specify o ring... I was stunned when I pulled it out of the packet but was heading to mountainsthat weekend so on it went... I cant believe the spares bloke gave me a non oring.... I cant believe I didn't ask !
BUT it has performed well with only one adjustment in six months (no real sloppy muddy stuff) so will probably change it soon as the weather breaks for nxt year. will be doing some road work on the kato so it will be fine.