What size motors will match up with my 1998 yamaha blaster four wheeler?

the motor on my four wheeler is now shot and i would like to upgrade the motor if at all poosible. i would even like to switch from a 2 stroke to a 4 stroke if that is possible as well. i would like to know as many different motors that i can put in it and what kind of results i would get with the different motors. i would like a faster four wheeler.