Mcculloch Mac Cat 440 Operator Manual
Most 2 stroke small engines are very similar. Unless you are going to take it apart and rebuild it, or replace the piston/rings and or cylinder, or do lower end work on the crank or rod, you should not need a parts/service manual for the saw. If it is a newer McC, (made by Husqvarna/Poulan), It will be difficult to find a manual, unless you know someone at a saw shop who can connect you up with the info.
Probably all you will be able to find will be an owners or users manual. If it is a newer saw, you will need to get a set of carb adjusting drivers (you can get a full set from amazon for around 20 bucks with shipping), as a lot of the newer consumer grade saws have carburetor adjusting screws that have goofy heads on them to keep joe sixpack from adjusting the saw to make it run correctly, as EPA has new engine manufacturers hog tied to be able to meet emmission standards, saws are usually factory set to pass emmissions, and thus do not run right, you cannot have both in an air cooled 2 stroke engine, IMO. Most always requires a bit of richening to get a saw to run as it should.
Even shops don't want to do it, as they can have fines levied on them by EPA or state clean air cops(DEQ) and the like. Most any 2 stroke engine will run on a basic carb setting of both low and high screws turned all the way in then backed out 1 full turn.
Mcculloch Mac Cat 440
From there it is a matter of tweaking the high and low screws a little in or out (usually no more than 1/4 to 1/2 turn either direction from the cardinal adjustent), to get it running well, starting easy and working correctly. Watch the videos, use the forum search tool to find more threads on saw tuning. There is a ton of info out there.
Mcculloch Mac Cat 440 Operators Manual
It is not hard to do, even if you have never done it. As far as gas/oil mix, I personally run 32:1, a lot of guys like 40:1, I only use 50:1 if I am using a real good grade of oil. Engines are not that picky on the mix, just don't do too little (leaner than a 50:1 mix), unless you are using a premium synthetic, like Amsoil). Best of luck to you.