I'm pretty sure it is. My future son-in-law is a mechanic with his own business - mainly car restoration but also the odd bike - and we were chatting just the other day about Chinese engines as he's got a quad for my grandsons (and their granddad) to ride around our garden. He said one he stripped down had so much swarf in the crankcase he was able to wipe it out with his finger! But he also reckoned that, if cleaned out and rebuilt properly, they can be made to run quite well. I still wouldn't pay good money for one though.