Stock 110 psi @ 8,000' cut the head .020"--call Doug at Doug's Balancing 303-922-7294 Check the carb boots for cracks. The hood will also develope cracks along the edge that meets the side panels if the hood is not closed right. Check Y pipe nuts--these require constant retorqueing, loose or missing clamshell springs, the skis are crap so don't worry about them 'cause you'll be putting Simmons on the sled, the rear suspension should only sag about 2" unloaded.
Ask the owner to show you the speedo cable--then ask him what kind of grease did he use to lube the cable. If he looks at you with a blank expression on his face, then you know the zerk never got lubed which means the drive shaft is probably dry = big bucks when it fails.
There are about 6 zerk fittings in the chassis that require lubing before/after each season. Flip the sled on its side an take a look
Have the owner remove the belt. If he doesn't know how, then he probably did not maintain the belt or the clutch. If he said the dealer did everything, ask to see proof. Check for broken belt pieces under the engine. Should be a spare belt and manual with the sled.
Remove the primary clutch and check the ramps to see if they are free and relatively free of belt dust--do not disassemble the clutch without using button clips.
Good luck,
Bob