That's Dax, you can find the link to the website on the left side of the screen, second from top. Good thing you asked, I bought my SD Stinger before finding this forum, not that it's a bad motor, but the Dax engines are better. Clean cylinders, balanced cranks, and Duane is a great guy. I've ordered all my spares and such from him, excellent results, fast shipping, all around awesome customer service.
I've got nearly 3000 miles on Tanglebones, mostly trouble free, so I can't say the Stinger is a bad motor, but after talking to folks here, and meeting a fellow with a Dax, I'm convinced. I was allowed to ride the bike, much less vibration in the seat and handlebars.
But that's two stroke. I can only imagine that their four stroke motors are also top of the line. I know Duane put considerable effort into designing a gearbox for the titan, if I'm not mistaken. That speaks to their experience.