Hello to all, and happy New Years! I recently bought a R3 for cheap and it has a different filter adapter on it than what I'm used to seeing, carb is date stamped 2002. I would like to know if this type of adapter is legal. Thanks in advance.
No, it is not.
Must be flat top with max 1/4" radius inlet.
The one in the photo is an old GEM filter adapter from the old days (way before 2007.) IKF continued to allow that adapter for a while even after WKA disallowed it.
Check with your local rules - most follow older WKA rules on the flathead still today.