changing and or adjusting the chain are the easiest things you can do to maintain a chainsaw
try doing it youreself to save some money
make sure that the little tension peg is in the hole on the bar and make sure the bar is seated flat before tightening completely
you may need to turn the tension screw a little to a loose chain position and once everything is in position
but before the 2 nuts are snugged up you adjust the chain tension
the chain
should not hang off the bar.
just right is when you pull on the chain mid way along the bar.. the bottom of the chain links should just barely show
too tight is when you use the saw and without the chain brake on.. the chain comes quickly to a stop when you take your finger off the throttle
that said, a chain can be sharpened many times before it is no longer functional
pretty much until the teeth are almost non existent
most importantly when sharpening a chain is to sharpen each tooth by the same amount to keep the teeth the same size
this will keep youre saw cutting straight
the easiest way to do that is with a grinder wheel made for chainsaw sharpening
at our shop we have 3 each set up with a different size wheel for the different chain gauges
they can be bought at places like (here in canada) princess auto
for a reasonable price... if you want to spend less you can buy a round file and sharpen by hand
same thing though you need to try to keep the teeth the same shape, and maintain the angles of the tooth
after a certain amount of sharpening by machine or by hand and the teeth become less aggressive
there are flat pieces of metal between teeth which determine the cutting depth and you will need to take a flat file and ever so slightly lower each of them
too aggressive of chain is more likely to kick back and may bog down due to biting off more than it can chew so to speak
sometimes a flat file to the bar to remove burrs from the sides may be necessary
there is a tool to file the edge that the chain rides along to keep the flat file(built in) at the correct 90 angle
when sharpening a chain on a grinder it is important to do this in tiny bursts of grinding with pauses in between
this is to keep the tooth from getting too hot and loosing its temper
if it is heated too much the metal will dull much sooner as it has lost its hardness
harder chains like carbide used by emergency personnel are unnecessary unless you plan on cutting through a lot of metal etc in the
wood
by dialing in the chain to the type of wood you are cutting you should get good results
i plan to get a diamond chainsaw for rock cutting (maybe)
but these more so sand the material away rather than cut it
anyhow hopefully i stayed on topic
enough and that helped!