Yamaha's base settings are a good starting point, and a decent compromise between several aspects of the sleds performance.
You need to ride the sled, and get comfortable with it. After that, start making small adjustments once you decide what you like & dislike. You might want lower gearing for better acceleration, or you might not.
There's a few things that you MUST do to not blow up your sled or get yourself stranded:
-Read the manual. The first time I had warning lights go on when riding, I was pretty confused. Even if you know a lot about snomobiles, Yamaha's are different.
-Get ice scratchers. You can't ride a mountain sled on ice or hard pack snow, even for 2 miles, without scratchers without destroying your hyfax. Inevitably you will need to ride on hardpack and you will wish you had scratchers.
-Carry a 2nd belt. It will break on you at the worst possible time.
-Carry a quart or two of oil. You'll flip the sled over and it will puke oil all over the place. You need to be able to refill it so you don't blow up your motor.
-Get a shovel. You'll get stuck, you don't want to shovel with your hands
-Get something to get you unstuck. If you ride with at least 2 other big guys, you can dig and muscle the apex out of most things. If not, you'll need a powder jack, sno-bunje, and lots of creativity.
It's a heavy sled. If you're stuck on a hill, it might take 2 people just to roll it down the hill. If you're stuck in a treehole, you'll need to roll it over, dig a ramp and drive it out at full throttle. That will take 3 people.
-Mark