I decided to put a new piston in my 2000 YZ426. I ordered a Wiseco kit from another web store, a new timing chain, and a gasket set. Once I had the old OEM piston off, I found that the wristpin and retainer rings sent with my Wiseco kit were wrong, too large in diameter. No way the wristpin was going to fit in the con-rod or the piston. The retainer rings were likewise too large. "Dang", I thought, "No way I'll get to ride this weekend... but what if I used the old OEM wristpin and the OEM clips?" Bad idea. The dimensions aren't right. Neither clip went in easily, probably thicker than the grooves in the Wiseco piston for the retainer rings, and the second one was harder than the first, probably because the OEM and Wiseco wristpins aren't equal in length...) I was a little uneasy, but I thought "...it might be fine..." Back together the bike started right up, and ran crisply. I felt a little less ill at ease. Then in the first hour of operation, the motor wheezed and seized up. When I looked inside, I found a cracked piston with one wristpin boss sheared off, its piston skirt poking through a shattered cylinder into the water jacket, and a bent con-rod. I have another cylinder I can get replated, but clearly I need a new crank, piston, ring set, wrist pin, clips, and gasket set. Easy $600 bill and weeks out of service all because I chanced it on a couple of $1 parts that weren't right. Feel free to pile on and tell me how stupid I am, or point out what else needs replaced because of my folly. I can take it. Perhaps one day someone else looking at a piston kit shipped with the wrong parts will pause for a moment because they read about this one dumbass who trashed his YZ because he wasn't patient enough to call and get the right parts. One can hope.