1986 honda fourtrax help!!

i have a 1986 honda fourtrax 250 and i just bought it today its in very good shape and did run fine i rode it for awhile but now its very hard to start and keep running and when i do get in to run the choke has to be open all the way and then it idles up very high and when i take off on it i turn the choke off and it will run for about a minute and then slowly dies I NEED HELP this is my first honda and im clueless so any info helps