My hubby had an '01 426 for 1.5 years, bought it new... not really enough time to test the motor durability, but he didn't have any motor problems. If I remember right, he put a clutch and top end in it for general maintenance after a season, but the stock stuff was pretty good. And he did shatter a rear hub after a year, which we ended up finding out was fairly common on that bike (lots of torque, crappy hub). So take a look at the hub and rear sprocket/rear sprocket bolts for any stress fractures/egg shaped bolt holes, etc. As for the motor, really all you can do is make sure it runs good/is jetted decent now... then plan on checking the valves every 6-10 hours, or if the bike becomes hard starting.