Lots of opinions about this. My general guidelines:
* Kawasaki calls for 10W40 weight oil.
* It should be motorcycle specific oil due to the oil lubing the clutch and transmission.
* For the FIRST oil change, use non-synthetic oil. It helps parts with break-in (even though new bikes don't need much any more).
* Full synthetic after. Kawasaki recommends 8000 mile intervals. I do it a little more often (5k miles, easier for me to remember).
The service manual link has been posted elsewhere but one more time:
I am kinda of partial to semi-synthetic oil. Seems that the the transmission works a tad bit better with some dino oil.
I did the recommended oil change at 600 miles and did the next one at 2,200 miles. Was surprised at how dirty the oil looked at the 2,200 mile change. Will do the next one at 4,000 and see how the oil looks then.
Did my third oil change at 4400 miles. Oil looked very dark at the 2,200 miles change. Oil this time looked good, like it could of gone at least another 1,000 miles. Using Motul (TECHNOSYNTHESE) 10-40 semi-synthetic.
Is there a crush washer or anything around the oil plug? Some vehicles have them, and others don't. I'm coming up on my first oil change on my 1K, and want to be sure I have everything before I tear into it.