A leak-down test is good but you should check the valve clearances and re-torque the head. The slow speed fuel screw tends to fall out of the bottom of the carb so check that periodically. Rumor has it the igniter box is different on the 02 with a dedicated starting circuit. OKIE has a new BBR kickstart lever which is easier and more effective to use. We've been selling a lot of the 2mm oversize Wiseco kits and people seem pretty happy with them, especially since its only half the price of an exhaust system!
Some other things to watch on the 01 YZ250F, crankshaft deflection. The crank journals wear and become loose in the main bearings causing vibration and noise. Thats more common on engines that are constantly overrevved.
Have fun with this excellent bike, Eric