http://www2.towerhobbies.com/cgi-bin...I=OSMG0010&P=Z
If you actually have a OS MAX and not the LA series, they will not have any parts at Tower. You will have to place a wanted ad in the classifieds? It may be cheaper to just obtain another engine?
Model engines, though they appear simple, have a definite technique to disassemble and re-assemble them. You need to get back on here when the time comes?
Enjoy,
Jim