Shineray xy300ste running problems

Hey guys, i bought a shineray xy300ste engine code lc178fmn, 300cc single cylinder, single carb and its having some running problems. most of the time it takes a while to get started, most of the time it will run for a couple of seconds then cut out but will eventually keep running. once started it will drive fine but after riding it for about 5 minutes if i stop it will stall and refuse to start again for at least 10 minutes. when riding there is no sign of a shortage of fuel or lack of spark though it doesnt feel very fast anymore will only do about 45mph.

so far i have

removed the carb and cleaned as best i can
replaced all gaskets and o-rings to irradicate any air leaks
gone over all electrics looking for dodgy connections
checked battery and voltages to componants
checked valve to rocker gaps (at 0.15mm not sure if this is right i have been told it should be fine)
checked engine kill switch
checked spark

i am fast running out of ideas and nothing seems to look like an issue or look like it could cause a problem. any help or ideas will be appreciated

Fixed, i replaced the igntion coil and spark plug. also the cdi unit had some corrosion/water damage inside so i cleaned it up as good a possible and have another one on order. so one of these things has fixed the problem.

These mysterious problems are, fortunately, rarely serious.

That engine is based from Suzuki GN250. 0.15mm NEVER recommended by Suzuki BUT loosen is way better that tight.

try and drain the carb to see if water is in the base of the carb, and do the same to the fuel filter....i had similar problems as you are having until i done the above, try it you never know