Hisun 500 issues

[ruralaus]

Hi everyone, this is my first post  regarding my Hisun 500. I bought it a short time ago thinking it was all fine, test drove it and no smoke and seemed fine. Got it home and took it for a run and instantly started to over heat (admittedly I didn't look at temp gauge when I was test driving it, I know stupid mistake), so towed it back to the shed let it cool and tried again and quickly started to overheat. Rad was stone cold and smoke pouring out the exhaust. Pulled the head off and gasket was blown, so replaced that and got the head checked for cracks etc and all OK. Replaced the water pump and purged the system and coolant now flowing, but still blowing white/gray smoke, although not over heating. Thought the smoke might clear so took it for a run and suddenly engine just stopped, towed it back again and everything looked OK, so ran it at idle for a while with no issues but still smoking, then gave it some revs and it stopped abruptly, started it again and same thing. Touch the throttle and it stops.

Any suggestions, as I am out of ideas? Only thing I can think is to take the engine out and to an engine builder for a full rebuild, but thought I would ask everyone here first if I am missing something obvious. 

Thanks