Put enough hours on an engine and something will let go. For this YZ250 two-stroke motor it was the crank after 250 hard hours. It made dreaded noises and came to skidding stop in the middle of the California desert. We feared catastrophic failure, but in the end it was simply roasted crank bearings. We contacted Hot Rods (www.hotrodsproducts.com) and ordered up a bottom kit, which comes with the crankshaft, main bearings and seals and a complete gasket set. It also included a Vertex piston and rings. We sent the cylinder off to Millennium Technologies for a re-plate (www.mt-llc.com). Here is a look at our rebuild of the engine. We highly suggest having a service manual by your side when working with any engine and good luck!