01-22-2016, 01:51 PM
Your oil didn't go anywhere, it's still in the engine, or oil filter, or oil cooler. I posted a thread about checking my oil a while back. To recap: Prior to a 150 mile ride my oil level was right up to the top line in the sight glass. After the ride the bike sat in my garage overnight, and I checked the oil the next morning before my next ride and it was down to the lower level. I know all about how to accurately check my oil so we won't go there. I started the engine and let it idle for a few minutes before shutting it down to recheck the level. After waiting a few minutes a second inspection revealed the level was indeed at the lower line in the sight glass, so I added approximately 6 fluid ounces to bring the level up to the upper mark. I put about 100 miles on the bike and rechecked the oil when I got home, and low and behold the level is so high the sight glass is completely covered. This over-filled condition remained until I did my next oil change, about 1,000 miles later, and it never lowered in the sight glass at all. So my conclusion is this: You can't depend on the sight glass for an accurate oil level inspection. Something on my bike was preventing all of the oil from flowing back into the crankcase so that an accurate measurement could be made. It is either being trapped in the oil cooler, or somewhere in the system, but it does not consistently flow back into the crankcase every time. One poster suggested this was related to a check valve in the oil filter.