another spark plug question and information

[double trouble]

I recently bought my newest project bike. The bike came with a flying dragon motor . The bike was not running well until I replaced the stock spark plug , which was a sino wx z4c gapped at .030, with an new/ old stock j6c marine plug with the same gap that I had lying around. The bike now idles and runs fine.
Here is where it gets weird. The j6c has a 6 heat range like the "recommended" ngk B6HS except the plug reach is 3/8. The sino plug is really what amounts to a hotter #4 heat range with a 7/16 reach and the B6HS has a 1/2 inch reach. Has anyone else had the head off their 48 cc angle plug motor to see which reach of plug is right?
Hers is a link to the sino replacement chart. It shows that the B6Hs is colder than the z4c. I Still am a bit confused . Which is the right spark plug?
http://www.sinosparkplugs.com/Replacementchart.htm

 

[Fabian]

Just grab yourself a projector nose NGK BP6HS spark plug for a baseline, then go either to a 5 or 7 heat range if the 6 isn't giving correct colouration.
On some engines a projector nose spark plug can contact the piston, so ensure the engine is below top dead centre when screwed in place, then rotate crankshaft through 360 degrees to ensure no piston to plug contact.

Generally a number 6 heat range is a good all-rounder with optimised jetting.