I spent three hours trying to get my just-completed Chinese 2-stroke bike to start.
It had fuel and compression. The spark was very weak, but there was a spark. All I could get it to do was to "pop" every now and then with furious pedaling.
Out of desperation I read through some posts and went out and bought an NGK B6HS plug at my local O'Reilly's Auto Parts store.
I installed the new plug, cranked the bike down the driveway and it started up and ran perfectly.
LESSON LEARNED. THROW AWAY THE FACTORY SPARK PLUG AND BUY AN NGK B6HS.
If the B6HS runs too cold (carbon deposits or dark electrode insulator) use a slightly hotter NGK B5HS instead.
If the B6HS runs too hot (electrode insulator is white, not tan, after hard running) use a slightly colder NGK B7HS plug.
Use which ever plug gives you a light tan colored electrode insulator when run hard.