Need some help with some info. I have a 2021 R1 I would like to put some race cams in it. I wanted to see if anyone knew if the race cams and valve springs for the 15-19 R1 will work on the 20+ ones. I have read on some sites that they will work but other sites said they will not do to some internal changes on the head. If someone can clarify if they will work on not it would be appreciated. I am looking at some used GYTR ones and I contacted them but haven't gotten a response back yet.
According to YEC, the 2015-19 cam part numbers start with 2CR, and the 2020-25 cam part numbers start with B3L. That doesn't really answer your fitment question, but usually when the first three characters are different then it's not a minor change. The fitment guide recommends stock springs for 2020+ YEC cams, and 2CR-A2110-71, 2CR-A2110-72 for 2015-2019, but does state that the stock 2020+ valve springs are interchangeable with 2CR-A2110-72 (2015-2025 kit springs). This information is not gospel, use at your discretion.
To my personal knowledge (had a 2015 R1M SBK engine and recently upgraded to a 2024/25 MA-spec SBK engine) the cams and sprockets are the same (latest YEC cams for the 15-19). I haven't measured them personally, but a reputable race team (in MotoAmerica) was also able to confirm this as I was spec'ing out my new engine build and figuring out which parts swap over. Not sure about the 2020+ OEM springs (though the kit manual says you're good), but I already had YEC/GYTR springs, and the air funnels are completely different (they physically won't fit in the 15-19 airbox and vice versa).
on the used valve springs I would suggest finding a builder or hobbyist that has a spring checker to verify they aren't fatigued. The cams are easy enough to verify lobe & retainer area wear with a visual.
