Heres the deal. I just did 5 days in Glamis over two consecutive weekend trips. I took my YZ426, LTZ400, and YFZ450. I primarily rode the YFZ450 and my girlfriend foloowed on her Z400. I estimate about 175-200 miles were put on each of the quads through some good dune rides. I changed the oil on all my bikes last weekend with the filters too and the Z400 and YZ426 were still somewhat gold in color. I also did the airfilters which passed the white glove test on the inside of the airbox boots. For some reason the oil from my YFZ450 was much darker then the other 2 bikes. It was a near black with a hint of graphite coloring. No metal flakes in the filter were found so it appears all is well. What would cause the difference in the color of the oil like this? Also, i run the same oil in all 3 bikes, but the YFZ450 was running straight 100 octane pump gas for the high comp. piston. Possibly some clutch material??

I believe clutch material also. Perhaps the 426 uses steels and the 450 aluminum discs which cushion the clutch a bit but also wear faster? My CR500 used aluminum discs and after 1 ride, the trans oil was dark black. My YZ400F still had caramel color oil and used steels.

I believe thats gotta be it then. Thx!

yfz uses steel plates and fiber clutches. could be you just ride the yfz harder. what kind of oil are you using?

Maxima Maxum 4 Premium 10-40

my bike's tranny oil looks like that too after every other trip.

i was told its a combination of the wet clutch contaminating the oil faster and the low volume of oil present in our tiny atv engines.