mikilon 250 valve adjustement

Hi, my son got a 2009 mikilon 250cc dirtbike in a trade a few days ago.
when ghe got it the bike wasent running at all, now i wonder what are the valve adjustements intervalls and clearance?
it backfires alot, will only run at high rews with choke. i have taking carb apart and cleaned it. I read on a swedish atv forum that the 250 cc water cooled engine suffored from a really bad carb adjustement out of the crate, not shure if that is true.Attachment 5075

Powered by water cooled OHC? Zongshen OR Loncin
ALL carb are tuned to EXTRA lean to scam emission law :naughty:

my cylinder and cylinderhead are silver and the lower part of the engine is brown.
I have found a all black Loncin engine that looks like mine. Mikilon engines are marked with Mikilon loggo. yes its an SOHC. Orion 36 looks like the same engine toAttachment 5076