hey im new here, tried other sites but no help.
my CHINESE crappy import pit bike (150 marshin) that i picked up for free, not running, is having a little trouble

i got the thing to spark into life after using a CDI and Coil off my brother's wrecked 125. bike started and runs fine for ten minutes or so, but if i shut it off, nothing. the bike will start with the choke on, but as soon as i take it off the bike dies, doesnt even try, just dies. but if i change the cdi and coil back over, it will run again for another ten minutes before same problem.
the bike originally was electric start, but i have taken the battery off as it was rooted. does the cdi or coil make a difference if it is off another bike?
could it be that it needs a battery to spark properly?
voltage regulator maybe shot?
i am new to bikes so any ideas on how to get the bike running will be greatly appreciated, took me a week to get it to start and i cant afford a new bike. please help!