40/1 is why it leaves oil on the power valves, it needs to be 50/1.
I run a repair shop and in the middle of the season i do 2 or 3 motors a week. Every motor i send out rebuilt is set up at 50/1 with amsoil intersepter. I have never had to redo any of my work they our all out there running and good. when oil in a 2 stroke burns it builds carbon, if there is not to much carbon it will burn and go out the pipe. WITH TO MUCH OIL IT WILL LEAVE CARBON ON THE PISTON. that is why you have oil on the power valves, it is not the oils falt it is yours for running it to rich. In my years of snowmobile repair in the last few i have seen alot more that the carbon burt the motor down. Polaris and cat both have there oilers to high I have ajusted many.
PS just FYI i have 6 mod 800 polaris rmks out there running 50/1 and none have any problems at all rebuilt a 2000 one at 5130 miles did not have to repalce any bearings on the crank just new pistons seals and gaskets. This motor has twin pipes, high comp heads, reeds, ported and bored carbs, runs 8300 rpm and has always ran 50/1 amsoil. that sled came back to me later with over 7200 miles with a bad clutch, one new clutch and back on the snow and still had 152 lb comp in the cyls and runs very strong.
My 2010 M8 runs at 29:1 per cat specs. With a high quality oil like Legend there is no carbon build up or deposits on the power valves or in the y-pipe. The motor is internally clean. I can post pictures if you would like. In the same sled running apv when I first got it (used) had oil dripping out of the can, oil spraying out of the y-pipe/pipe connection, and had to clean the power valves within a few hundred miles.
So I guess it could be said that if you want to run legend you could leave your factory oiler set at factory spec with no problems and more than likely not have to clean the power valves for several thousand miles.
Or run synthetic/semi-synthetic/traditional mineral oil at factory oiler specs and clean the power valves regularly (not to metion the other problems assoiciated with runnig synthetic oil in a 2 cycle engine) or adjust your oiler out of factory specifications and risk warranty issues. I asked my dealer about running 50:1 with the oiler and there was laughter. Now I can say that the ski-doos I have owned have been closer to 50:1 with the stock oiler. But longevity is not a strong suit for the newer ski-doo motors with top end failures around 2000 miles, I as well as many of my friend's can attest to that.
Another thought to keep you entertained. the same engineers who "design the new motors for synthetic oil" are more than likely the same engineers who designed the Polaris cranks, Polaris 800 top ends, the ski-doo single ring piston, etc, etc. etc.
Jason