Ms 210,230,250 fully adjustable carb is what you want to upgrade the 170/180. 171 is a stratto saw and carb is different. Far as rebuilding the stock carb they rebuild like any of the other ones are no harder or easier. The zama ones will be a c1q body if I remember and internally the same as weed trimmer carb or 271/311 ect. Otherwise if older could be a walbro with fixed jets in a wt series which are all similar inside. But i definitely would go with an ms 250 carb so you can adjust it. Also the 170/180 are actually tough little saws it may be boggy also from a plugged exhaust screen so check that also. May run just great after the screen is cleaned or taken out, if you just remove the screen it won’t change the flow enough to make it lean out.