the glory of a blaster is that no motor problem is expensive.
sounds like its just in need of a rebuild like mentioned above. rebuildign the top end is a simple job if you have the tools to do it. maybe even recruit a friend with engine experience to help make it a little faster. a top end rebuild can easily be done over 1 weekend and should be under $100. you can go to an autozone and rent a tool for compression testing. it should cost only like $5 to rent. its pasically a air pressure guage thats connected to a fake spark plug. you put in int and kick the engine over. it tells you the cylinder pressure from there. it should read over 100psi. if its less than that you need a new piston and rings. be sure to get a top end gasket kit as well.
now, as far as trade goes. yes, you have a cheap pitbike made from chineese parts. i used to have one for my kids and while fun, it broke alot and parts were a pain to get. the blaster will last you years and is quite reliable when taken care of properly. plus its much faster and has a TON of aftermarket upgrades and replacement parts on ebay. i would trade that in a heartbeat. it may take a little time and $$$ get get back to normal, but once you are there it will be more fun.
