stock sled for 0-2000' right now it has 390's just wondering if that is right. polaris specs reccomend 450's. planning on putting the slp air box and mbrp can on. what jets would i need then.

you can go to your dealer and they have a book that will show jettings and needle settings for that type of sled, with a gutted air box and can you will probably have to go up two sizes on jets and drop the needle one slot.

Needle middle, 420 mains.

if that stock or with the box and can

Derek,

The can won't change your jetting at all. I'm not sure about the airbox, on the Pro-X's it actually makes the fuel mixture richer so I would assume it does the same on the RMK's but I'm not for sure. SLP says to go 2 jet sizes richer just to cover their ass basically. 420 main jets should be fine I think with or without the can and airbox mod. Pockets knows Polaris sleds pretty good so I would wait for his word.

Pockets,

The owner of this sled is a friend of mine and he just bought the sled. The previous owner said he was using 390 main jets when riding around 1500 feet and 340 main jets for the Black Hills(4-7K feet). That sounds really lean to me even on a completely stock RMK 700. What do you think?

Yes, 390 sounds lean to me for low altitude. Unless it was 30F and warmer, then he would be in line with 390 at 1500 ft., and 340 at 4-7000. You told us your about your airbox and can, and that was taken into consideration when I responded the first time.