At idle, anything from 4 BTC to 14 BTC will idle just fine. I use about 10BTC usually.
At cruise, you want about 40-50 TOTAL Timing, including initial+mechanical+vacuum advance. Less than 40 will run ok but run hotter. Much more than 50 will start to skip and buck.
At full throttle you want about 32-36 total at say 3000-3500rpm. I never go over 40 total mechanical. No vac advance at full throttle so that isnt counted.
Could also be a sick carb or ignition, or a leaky intake gasket or valve or lifter acting up.
