Nice build indeed very clean i agree with bikeguy joe I to think it is the russian engine i read a thread on those apparently they were produced from mid 50s til 1990 and also the guy that posted the info said he believes that the chinese r a knock of of those russian engine and posted pick to back up his statement and i couldnt agree more its incredible how close of a design it is the only real diffrence is the carb hook up to the crankcase instead of the jug on the russian engines