Sorry, but I don't know what a "lay shaft" is. The BW200 Big Wheel (used ATV tires) had a jackshaft on the swingarm, if that's what you mean. There was only one bearing in the center, and a sprocket on either side, and that bearing was prone to wearing out.
Unlike the XT225, which has a single bearing supporting the sprocket on the inside, the TW200 has an outrigger bearing in the sprocket cover, which is lubricated with engine oil. I have never, ever heard of the output shaft failing on the TW's. It's supported on both ends of the sprocket with bearings, and should be good forever.
Also, the TW is one of the most reliable engines Yamaha ever made. Big beefy roller bearings rely on oil splash - not oil pressure - for lubrication. The bottom ends never die, and so long as you change the oil every now and then, top ends are indestructible.