sounds like you brought a baja that hasnt been maintained...
its not a problem though..
if i were you i'ld set a side a day and pull ya engine out,
get a new pullstart they're cheap enough,
clean airfilter well, and reoil,
inspect ya gaskets between the carb and inlet,
inspect ya plug and change if unsure,
re set ya coil gap,
inpect for gaskets blowouts,
inspect fuel tank and lines for spits/leaks, clean clunk filter (inside tank)
refuel with fresh fuel and good 2stroke oil.....

its a real de-motivator when ya engine just wont play the game
so take ya time to get the engine to start and run reliably and that'll help keep ya pullstart from braking often

good luck