Yes, Chinese cylinders, I had an early 400KQ with a blown a big end, wrecked the cylinder and did other damage. Getting a new big end fitted to the crank cost an arm and a leg, and a new cylinder from Suzuki would have brought the bill to more than the bike was worth. Rebuilt it with a Chinese cylinder kit and it knocks. No idea why, faulty piston, or the machine shop that fitted the big end got it slightly wrong, or me, who knows? The owner has the mechanical sympathy of a Gorilla, so he wasn't bothered and it has knocked away happily for over 12 months. On the other hand, had a 250 Honda with a worn max oversize cylinder, so got a Chinese kit and it has been fine.