Kawashima san, thank you for the detailed analysis. I agreed with your assumption of W400 having a lower ground clearance of 5mm compared to a W650. I scraped the left side of the center stand during a left turn. The left side of the stand will touch the ground before the left foot peg’s feeler. No problem at all for the right side. I will post a photo later to show you the scraped area on the stand.

Can I have your email address Kawashima san, I have a few questions regarding the W650 engine.

Some updates on my W400:

I have bought a copy of original Kawasaki Service Manual (English) from Japan. As shown in the photo, I also installed a Kawasaki rear rack and a W650 center stand on my bike.

Wow.Center Stand is nicely installed. Rear rack is also very useful option for additional luggage.
Pure black is nice color. Thanks for the updated photo!