So, I got to wondering about this whole YZ crank thing. Personally, I've blown up more KTM cranks than Yamaha ones but that's neither here nor there. I looked up the part numbers for an 18 YZ and a 16 YZ and they take the identical con rod and the cranks are the same part number with the exception of the series ie: BR9 for 2018 YZ and 1SL for the 16. There is a revision on the 16 actually 3 of them, but when a part moves forward in the Yamaha world the revision resets to 00 to go along with the new series ie BR9. So long story short, same crank.
I just received my parts order for my 2018 YZ including a new crank, if you are splitting the cases buy a crank, full stop, why would you not? It will be interesting to see what 170 hours of snow biking has done to it when I tear it down. I think the crank is fine, it measured perfect at 80 hours, doesn't matter it's getting a new one anyways. I'm dead certain the trans is pooched as I basically have no 2nd gear. I've got a 2020 trans to put in it and I'm adding an FX OD 5th gear. I would be a lot more concerned about an 18 or 19 YZ trans than I would about the crank. The 3 cog gears were all redesigned in 2020 on the YZ. Yamaha knew they had a problem in 2018 but didn't want to admit it.
The KTM 500 and the Husky 501s cranks seem to last forever but those bikes are like running a diesel, they don't rev.
M5