If you sit the bike on the grab bar when washing/cleaning it happens. I'm gonna modified the intake that instead of recycling the oil thru the intake tube it will go into a catch can then back into the motor.
there will always be a little oil in the intake tube(stock) that is why it is designed with the small sump in it, this is from the oil draining down the tube when the engine is shut off, this oil on the tube was previously suspended in air and sucken into the intake tube via the crank case breather tube
Check your oil level. I did my first oil change and put the level at the top of the sight glass and that is too much. Your oil level should be about a 1/8" above half sight glass. I keep the oil level there and no more oil in the intake. Mine would even get enough in the tube to smoke on morning start ups. Fixed the oil level fixed the problem.
How much oil are you putting in on your oil changes? I have the same problem but i use a ratio rite to get the exact 1.2L with filter removed. And the glass never seems right. This is my first bike with the glass. I though it was nice but i dont know for accuracy. Also are you doing your glass inspection when the bike is running or not? thanks
I dont know how much exactly but I add till its 3/4 up the glass then start it for about 10-15 seconds and shut it down and wait about 5 mins. and add till its alittle over the half point. check again later. I keep my level there and have had no issues.