Harley freely sells crate motors because they know they're a "consumable" item on their bikes, like tires or brake pads for anyone else.
Yamaha builds their motors to last and always have. I've seen a Yamaha 2-stroke snowmobile engine run, for 50 miles, with a HOLE in the cylinder. Didn't have much power, but it kept the sled moving to get back home. Rebuilt it for $150 worth of parts, good as new for another 25 years. I also have a '90 Blaster that's had the piss beat out of it for 20 years and the little 200cc single still starts first kick every time and runs like a top. My Yamaha RX snowmobile has been held WFO for miles at a time with absolutely no problem, as a polaris next to me blew it's motor trying to keep pace. My Max has been held WFO for 10 minutes straight at ~145mph, not so much as a hiccup or fart in protest, the temp barely rose 10 degrees from normal.
Yamaha builds the best powersports engines on the planet, bar none. If Yamaha made cars, I'd buy one.
