While I generally prescribe to the theory that "it is your sled, you can do whatever you want to it", the philosophy of oil addition is one that can generate some strong opinion. I for one would really like to know what the Kawasaki engineers were thinking when they built these engines as there are some things about them that I don't immediately understand, and even after a few years of playing with them still don't understand. For instance Invaders and Intruders are essentially identical. But, there are side shields on the crank of the Invader but not the Intruder. Why is that? Also, the Invader gets an oil line to the center of the crank case. Why not to the right and left side bearings? Lastly, for the cranks that I have disassembled, I cannot find an oil path from the outside of the crankcase to the inside of the center seal. By the grace of God these conundrums do not keep me awake at night. And regardless of the reasons, they seemed to know what they were doing. Many, too many, of our sleds have come to us with the oil pump disconnected and residue of pre-mix in the carbs. We take them apart, replace the crank seals, put in some new pistons, use new carb boots, and hook up the oil pump and away we go. We have found one or two bad pumps on sleds that were really abused. But in the final analysis, all of our sleds run on the pump and I have never regretted not needing to mix oil and gasoline.