I used to try sell restored equipment too but all I got was insulting offers. So I quit trying now people are wanting to know if got anything for sale but sorry I don't as I part everything out now. I am not spending my time and money repairing a piece of equipment just to be insulted.
Funny thing my brother could half a## repair them and sale for the same price as the ones I tried to sell and mine where much better condition.
Kawasaki does spec SAE20w50 or 15w50 full synthetic for those engines but that doesn't resolve heavy smoking of a worn out engine. Matter of fact I just got in 5 gallons of the Kawasaki synthetic oil with zinc additive so it can restore some of the cylinder damage.
I spent years in sales. Everything from Houses to Kirby vacuum cleaners. My sales rate is probably 90%.
The John Deere I picked up from the scrap yard, with the intek pro, is one butt ugly mower. But it was only $20. The paint on it is about as bad as I've ever seen. But I have three people lined up for it, when I get the deck finished up.
Picked up a good Husqvarna z246, two Husq trimmers, two chainsaws, a homelite trimmer and a backpack blower for $300 a couple of weeks ago, from someone getting out of the lawn care business (lol before the season started). Already have $700 profit on those, and still have 3 left to sell.
I sold the zero turn way to cheap. As soon as I listed it ($900), people on facebook were fighting over it. First one here, with the cash, live 1.5 hours away.
There's good money it them, all season long. During the winter, it's a great time to buy them dirt cheap, and fix them up. I wished I had 20 riders right now, cause I'd have them sold in a couple of weeks. At an average of $350 each profit, with usually less than $100 in parts and 1 to 2 hours labor, how can you turn that down?
This Kawasaki, if it was ring damage, or anything else, changing oil viscosity wasn't going to change much of anything. BTW, the one who said to change the oil, didn't even know what oil was in it, when he said to change it. The one who posted the video didn't list that information. I guess the point of this, was on that facebook page, about 90% of all the advice is just guesses, from people who don't work on them.
You know the type. One's that pay more attention to the comic strip of Taryl's skit, than they do the information he gives.