This is a good point.
And it's obvious Erik is sick of answering that question. He says the motor he uses is an all-new design that is perfectly suited to Buell's needs, but he also complains about how heavy it is.
I have a few theories as to why Buell isn't going to have a different engine any time soon:
-The close ties to H-D require them to use an H-D motor, and the VR water-cooled engine is too heavy and complex for use in a sportbike.
-More power would change the character of the bike and alienate the customer base who likes the air-cooled, pushrod thing.
-This motor burns clean enough to meet Euro and CA emission standards for the foreseeable future.
-A more complex, high-performance motor would be more expensive, requiring Buell to either charge a lot more money for their bikes or reduce the quality of the other compenentry.
I think Rotax, Folan or KTM could build a fantastic motor for Buell, adding 10-20 HP and dropping 40 pounds or more, as the motor could be used as a stressed member. But it would be a lot more money and wouldn't have the same charming character these bikes do now, and it still would be no match for machines like the GSXR1000, so why would they want to build it?