I am planning to do my 1st ever top-end. I have a 87 and 89, 250 Mojave. I have been seeing a lot of pistons on e bay, which one is better? Wiesco, High Performace, Namura, Athena??? Also, what should I look for when I remove the original piston? Should I bore it out or not? Also, is this hard to do? Anyone have any advice or tips? Anything will help, I never even changed the oil on a ATV! I have taken my quad to shops and they want to charge me $600 to do a top end! I just can't afford that! I have 2 Mojave's that have the same problem, it's the way I bought them. Both quads still turn over. I will take all the advice I can get. Thanks to all of you for help. And any suggestions on gaskets?