Mcculloch mac 120 chainsaw manual - Standard Oregon Chainsaw Chain For Mcculloch Chainsaw 18" Bar Length 64 Drive Links 3/8 0.05 Gauge Chiesel Chain

SOURCE: McCulloch 120 Chainsaw Owners Manual

If you need the parts manual for that saw, heres a link:
http://www.mymowerparts.com/pdf/McCulloch_Parts_Service_Repair_Manuals/Gas_Powered_Chain_Saws/

SOURCE: The second hand McCulloch 120 chainsaw I purchased

I think the pre-adjust settings are to turn jets in all the way and back out 1.5 turns each. then:

You will find a Low and High adjustment screw. At idle turn the screw in or clockwise until the rps starts to decrease. Then start turning it out till you hit max idle rpms. Turn screw back in a quarter to half turn and it should be idling smoothly. Be careful here and get someone to hold saw if necessary but hold in throttle to full speed and do the same with high adjustment screw. turn it in till rpm starts to drop then back it out until you get to max rpm and it won't go any higher then turn it back in a half a turn.