hello out there ive been sledding and repairing them for 20++ years now ! so you are looking or bought a sled off of e-bay or a dealer . oh boy here we go if possible (( pay in person)) on the sled for one !when you go to pick it up  if it sounds to good to be true it is probally a scam ive ran into a few on here and locally .. ok when you get there please inspect the sled just dont load it up and go ive heard horrer storries about people buying a sled and it came down to they were worried about there feedback pishposh look it over . #1 over all inspect the sled look carfully at the hood belly pan and stand back and see if the tunnel is twisted or sitting at a angel if it is walk away . also if the running boards kinked and bent up look at the main frame if its cracked   .  #2 push on the front end and see if the shocks colapse and rebound nice should be resistance there not like jellow the rear suspention also if it colapses and stays down figure a new shock .  #3  slides are worn , track clips and track , ok track over all (( my opinion )) if its been studded dont buy it . you can always stud a sled your self or buy a vantage 3 cut for studs track if its cracked or worn well a few seasons riding yet , ripped out studs figure a new track . #4  if the milage is low look at the grips and running boards if worn accesivly might have more miles than it says . #5 ok open the hood  . take the belt guard off  ok look by the back of  eng. clutch or main , see if there is oil there seeping out of the main seal , grab the main drive clutch top to bottom and left to right  if there is any movment in these directions ((rebuild )) now  if the clutch moves side to side(( clutch and rebuild )) the clutch  wiped out the seal and what not . common on polaris , cat , around 3 to 5 thow miles . the 2ndary see if it moves back and forth should slide outward a bit but not up and down  jack bearing is out if it does so ..turn it without moving the track there should be play but not much maybe a 16th inch to 8th in if more chain is loose .(( i found out the hard way on this one on my yamaha srx )) these need to be checked often 500 to 1000 miles re tighten your chain turn in finger tight back off a quarter turn . if this was never done it will wipe out your track drive bearing on all newer yamahas you will need to ask if its ever been done if not and has 3thow miles track drive bearing !! can be aplied to all sleds ..  pull dip sticks check for shavings . ok #6  this is important pull the plugs if you have a gage check compression also inspect plugs should be black or brown not white . not to knock these sleds polaris tripples and skidoo tripples be very cautious and yamaha twin 600 and 500 cc  you will be needing a compression tester  usually the middle cylender on the tripples and the clutch side on the twins will have hardley no compression if you see 100 psi or less rebuild ,,((most sleds are around 145 psi )). you can also check compression by slowly turning it over with your thumb over the plug hole if it blows it off it (( might)) be ok but a tester is best policy for accuracy. also look for coolent in the bottom of the belly pan common on cats pump is out toatal tear down to get at pump most others have external pumps hose clamps on others .   #7 ok if you can tip the sled on its side check for play in the track drive up and down  if there is bad bearings . shouldent move only turn . if it passes all these tests its most likly a good sled . now ((not)) all dealers go threw a sled so dont take that for granted eather . thanks for reading and good luck with your new sled .