Biker Boyz [Region 2] (English audio. English subtitles) - Amazon UK English subtitles)
Keep both the video and the .srt file in the same folder.
This is generally the most reliable source for specific movie releases. Search for "Biker Boyz" and look for the entry that specifically mentions the "YTS" or "YIFY" rip in the description.
If you are streaming the movie, services like Amazon Prime Video or MGM Plus provide official English subtitles built into the player.
Biker Boyz streaming: where to watch movie online? - JustWatch
You can search by the exact file name Biker.Boyz.2003.720p.WEBRip.x264-[YTS.AM] to find a direct match.
The official YTS subtitle page often hosts the exact SRT files for their own movie encodes. How to Use the Subtitle File