Timing advance

[Honda 250r 001]

i got me a 310 big bore and i cant decide if i should advance the timing any on it. I was running +4 deg. before i put the big bore on and i was running pump fuel. Is it a bad thing or does it help that much? I have 190 comp and im running 100LL aircraft fuel. I am setting up a mid-top end motor.
Thanks