I just got a 1991 Polaris 4x4 4 stroke ATV and can't tell what it is trail boss or trail blazer??
Help??

 

You don't say if it's a 250 or 350 water cooled atv.Look on the right frame down tube for the model plate. Plus the Trail Boss(1991 ATV TRAIL BOSS 250 - W918527) and Trail Blazer(1991 ATV TRAIL BLAZER - W917221) were 2 wheel drive models.
1991 ATV TRAIL BOSS (350L) 4X4 - "W918139"
1991 ATV TRAIL BOSS (250) 4X4 - "W918127 "
Plus no 4 strokes until the Magnum 425 came out later..

 

It's a 250

 

Then should be the W918127 model. Good machines,still a bunch putting around. Here's Polaris Parts website.http://parts.polarisind.com/Browse/Browse.asp Just click on the year model and you can see. Plus several good online places Like Cheap Cycle Parts,Partzilla,etc for parts along with ebay if needed.