Additionally, many of us are aware that black oil does not mean bad oil. The problem is these engines destroy oil. They don't have a lot, they run the oil hot, and they shear it to nothing rapidly. MX on a 450 will shear Rotella 15w-40 down to a 20w within ~5 hours.
Conservative riding on bikes that hold a lot more oil (Say, older YZ250Fs) can go alot longer on an oil change.
I only picked 50 as an arbitrary number. These seams to be a big spread as to the thoughts on piston replacement.
Change the oil every 5-7 hours, piston every 100,
EIther way the idea is to find out if it really does need to be changed that often. Granted my sample pool for the experiment is small... 1.... but I hope to see some good data.
I have never used shell, and will never use shell, Saw to many motors come in with excessive motor wear and despot build up running Rotella. in once case I worked on a motor where the computer logged that the motor had good oil pressure, but still seized. at tear down we found that the motor had almost no oil any where... but the oil pan. come to find out that deposits had built in the oil passages and clogged them AFTER the pressure transducer and caused the motor to run dry with out the computer knowing it. Go figure they where running rotella. sorry but that oil is sub par in my book. I don't want to start the amsoil war but I have been a user/dealer sense 1998. I run it in every thing from my generator to my truck to my cars to my toys and have never had a blown motor in any thing. I use 0W-40 because i run in a cooler climate and often start ridding while there is still frost on the ground in the morning. as for the filter I always use the WIX. I'm not sure what stock filters, filter down to but the WIX Ea filter goes to 10-12 microns. I laugh when i see people run the stainless steel one that is only good to 34 microns. Particles as small as 2 microns can damage a motor and if the shear really is as high as you say it is then filtering as low as possible is of paramount importance. there is a balance thought, to small and you sacrifice oil pressure. After starting this thread I found an oil cooler that I'm going to add to the bike also. On that I may add an oil pressure gauge or at least a port for a gauge to be put on for testing.
I'm ordering the Jagg Cooler as I type this. (here)