If you are interested, I found 2 complete engines. a 2006 for $750 and a 2007 for $800 + $100 shipping from Kentucky. Or if you are interested in rebuilding, a complete lower end for $475 free shipping from Missouri, and a set of cases for $175 free shipping from Penn., but you would have to get a new crankshaft from Honda for about $270.00
Using used parts, the motor could probably be rebuilt for $850 with the only guarantee being against defective parts. Keep in mind that these motors are push-rod valve train motors. They are considered
utility engines
NOT perfromance engines. I'm guessing your motor exploded due to high RPM use. If you are trying to run this machine on a track, I would recommend salvaging it and getting a sport model that is more suited to the way you are using it.