Howdy,
I have a pet procedure for break in of a brand new saw:
First, I make sure I have the best possible gas and mix oil as per the factory recomendation exactly.
Then I fire up the new saw, avoiding an initial race for just a minute, and make sure it is set for reasonably correct idle. Then I check the high end, very briefly not to adjust.
Then is set the saw in a previously made bore cut in a stump or fence post, and let it set there and idle for several minutes, observing on occassion to see if it is loading up at idle. If it does, (most do) I take it out of bore cut and rev it up enough on highspeed to clear it, and to check the high end setting, should blubber a bit. Definitely do not let it scream. Then I put it back in the bore cut, and let it idle out the tank.
On the second tank, I check the high end and make a cut or two. Important not to work the new saw continuously right at first. Heat is the big enemy. A really good quality saw will be a might tight and hotter running as brand new. Looser saws, are made figuring most people are not going to break them in correctly. I take the breakin very seriously.
Personally, I follow the same procedure even if someone has brought me a new Poulan or weekender Husky. (A few folks around here do, just to be sure they get off on the best foot. I give a lecture about fuel and storage, and guess what? Those people do not have trouble and the saws seem to last indefinitly).
The correct thing to do with an 026 Pro Stihl, according to Stihl, is to have the dealer rejet the carburetor for this elevation. (2,500 - 3,000 ft.) Personally, I don't like this, as it will be too lean if someone takes it to the coast. I'm testing that suggestion from this forum about substituting Tillotson HU40b. I am having some Stihl pros do this on the sly. (I'm sure Stihl would have a hairy fit).
Regards,
Walt Galer