Standard GXH50 has always been 2.1HP @ 7000RPM. HS49 (142F I'm referencing) power figures are almost always inflated. They have less compression, sloppier engine tolerances, and an inferior con rod than the engines they are cloned from. Performance upgrades are extremely limited because there isn't a removable cylinder head and the whole thing is splash lubed anyway. If you raise the the spring compression to eliminate valve float, you end up wearing out the plastic camshaft quicker. Extended 8+K RPM running will "bronze" and then shatter the con rod. For the money tho, the clone is awesome. The Honda cost over twice as much, but it's not twice as good.
This new one is overhead cam, so hopefully we get a real metal camshaft and a nicer oiling system. Funny thing about some of the small clones is that they are pushrod and not OHC and often have the smaller displacement of older Honda engines (HS31 vs GX35). The GX35 is, IMHO, an amazing engine. It's quiet, compact and actually has quite a broad powerband. It also has a superior oiling system and therefore higher angle-of-operation.
I have an old Mongoose full-suspension MTB that I've been thinking about building a rackmount with..I'll be eyeballing this hard!