===================================================================Yamaha were putting reed valves in road and dirt bikes for over a decade before they put them in their hp-is-king 250 road race bikes. The RD250 had them 12 years sooner than the TZ. It's a reasonable bet that Yamaha knows far more about two strokes than everyone on HBA?
Knowing How to Build Good Engines is done by most of the Engine Companies, but Marketing those Engine Products is two different things, just as Making the Engines that People really want. In the past, Companies listened to what People/Racers wanted, today they tell us what they decided to give us and at these much higher Prices. If we look at Sled Sales, in 1971 was the year the most Sleds were ever Sold in one year about 585,000+ with about 4 Billion People in the World. In 2016, all the Sled Companies that are left(Yamaha, Skidoo, Polaris, Arctic Cat) and I think there is a brand in Russia, but they only Sold around 185,000 total with almost 8 Billion People today! It doesn't take a Marketing Genius to see whats happening. If these few Companies hadn't diversified into other products, ATV's, Jet Skies, etc., they would have went bankrup. Actually, Arctic Cat I think did file bankrupency once a few years ago. But most of these Engines are pretty well made if taken care of, it's the Human abuse they have to suffer from.
The Sad thing about many Companies, whether Snowmobile(400+ at one time) or Airframe Companies(750+ at one time) they rely on Engine Companies and vice versus! Kawasaki, Yamaha, Suzuki, Honda, their roots all come from Motorcycles where they made both their own Engines and Bikes. Arctic Cat relied on Sachs, Kawasaki, Suzuki, for Engines, and just started making their own Engines about a year ago. Skidoo relied on Sachs and then Rotax and finialy bought Rotax out. Honda has never made a Snowmobile/Snowmobile Engine or Ultralight Engine, I wish they did, they make some of the best small engines in the World. Suzuki made some Sleds, but never made any Ultralight Engines. Some People say, Suzuki Sled Engines were even better than Kawasaki Sled Engines, but both were good Engines if maintained right. Rotax held 85% of the Ultralight/Kitplane 2 stroke market at one time. In the USA, Rotax and Kawasaki Engines were used the most. Kawasaki sold their 340/440 Sled Engines also as Industrial Engines so were easy to buy for Airframe Manufactures and cheaper than Rotaxs 377/447. There was never a Good Tuned Pipe Designed for the Kawasaki's or they would have sold more.