Try doing a compression test before going any further with speculation.
There are hours and years of experience that I could write to try to explain this in more detail but the bottom line is the engine is in need of repair.
Whether that involves a new head, whole engine, or whatever your heart desires in upgrades and projects, the best place to start is with tests to determine what it needs. The fine points of where you want your project to go from there is a matter of making decisions...there are no wrong decisions, really, but there are many possible paths and outcomes that can either make you a happy and more confident Ranger DIY or otherwise.
There are many build and engine upgrade threads on here if you are not sure where to go...read my oil catch can epic investment of time and energy that just about drove me crazy...but it certainly was entertaining for me even though it cost me a bundle.
I'm not at all trying to dissuade you from playing with your new toy...merely trying to guide you towards a faster solution that won't cost you a ton of money and effort...read the last post in this thread for the final summation of two years of efforts and how I paid for an oil executive to educate two or three of his children...probably to PhD level or at least post graduate studies...
http://www.therangerstation.com/forums/showthread.php?t=131097