1200 choke wont stay out.

recently i had a new choke cable put on because the s****tster because
it wouldn't stay out. it worked great for a few weeks now its doing
the same thing.  you pull it out and you have to hold it, if you let
go it slides right back in. ive tightened the compression nut all the
way down and it still wont grip the cable hard enough to hold it any
ideas? its not a major issue right now because of the warm weather but
when the cold gets here this will be a "pita" again. i know i can just
stick a clothes pin on it but id really like it to work correctly.
thanks in advance.