Andrew McCarthy rides a Harley Davidson 883 Sportster in the movie Mannequin, released in 1987. I believe the Sportster is a 1986 or 1987 model and its powered by the Evolution engine which had only been in production for a few years at the time. Harley Davidson was recovering from almost going bankrupt a few years earlier so having this new Sportster in a major film must have been a much needed advertisement for Harley Davidson.
You can see the film Mannequin, for free on archive.org (see link). I'm not sure how long it will be there, but even if its gone by the time you read this there are other websites streaming this movie.
Watch Mannequin here:
https://archive.org/details/mannequin-1987-romantic-movies-2020-full-movie