Lbs

The plug was replaced before I replaced the rings but i pulled it out this morning and it is pretty black so i gonna replace it and see what happens but i also forgot to mention he said previous mechanic replaced everything to do with spark also before i got it was out of time but i did time it back correctly when i tore it down

Ok customer brought me a 2000 Yamaha 250 idles great and will run wide open but when you take off from a idle it tries to die and sometimes will die said took it to a mechanic he put a different carburetor on same thing took to another mechanic swapped carburetor again same thing so he brought it to me i went through all 3 carburetors cleaning, adjusting same problem i checked compression only had 90psi so i put new rings, piston, and jug on now have 155psi with same problem any ideas?z