What year model vin 1563339 polaris 250 trail boss

Check the link and ATV Forum

https://www.google.com/search?q=1985+Polaris+250+Trail+Boss+won%27t+start

..

2 stroke no valves.

https://www.babbittsonline.com/oemparts/l/pol/5034200bf870023468a7390d/1998-trail-boss-w98aa25c-parts

Is the engine a two-cycle or four-cycle? A two-cycle engine requires oil to be mixed with the fuel to lubricate the piston/rings/crankshaft/rod top and bottom bearing/main bearings.
A four-cycle doesn't require it. (A four cycle has valves in the head)

https://searchmanuals.net/search7/?keyword=%2Bowners+%2Bmanual&gclid=Cj0KCQiAzePjBRCRARIsAGkrSm4hwGgMJ4loxVKnk_d9loNSyMnzjcinCTYKx6DBNotuk4W7EdNURhoaAggqEALw_wcB

Here are a couple of posts.
Polaris trail boss fuse box location
This is different year but might help,
http://atvconnection.com/forums/polaris/336771-06-trail-boss-330-a.html

DOWNLOAD POLARIS TRAIL BOSS REPAIR MANUAL

trailboss-manual.blogspot.com/
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if thats a cvt model maybe your shift lever is out of adjustment

A 250 probably doesnt need a cooling fan unless you're hauling heavy loads slowly in hot weather.

hope this helps , it's a free download of a complete repair manual for the Polaris 2004 Trail Boss 330

http://www.gobookee.org/2004-polaris-trail-boss-330-service-manual/