We recently bought a well-used late-model YZ250. Though it had been well maintained by the previous owner, I was surprised by how much wear it had, and where that wear had occurred. This thread is not intended to be so much about things to look for when buying a used bike, but how to refresh a high-hour, high-miles bike. Please feel free to add any additional observations or tips. REAR SUSPENSION BEARINGS: Pay attention to the swingarm pivot thrust bearings. These bearings are positioned right behind areas on the frame where water can accumulate and sit unnoticed. While most of the other bearings may appear to be holding up just fine, the thrust bearings generally rust out early. REAR SUSPENSION BOLTS: While the rear axle has two ‘flats’ machined on its end – to allow you to spread the wear by flipping it over -- the suspension bolts do not. This leads to the load and wear being continually placed in the same area on these bolts. Grinding a new flat opposite the factory flat will let you flip the bolts over to expose unworn bearing surface. Its like getting fresh pivot bolts for free! STEERING BEARINGS: The seal for the top steerer bearing on aluminum-framed Yamahas has always been too flimsy to really do its job well. Expect to re-grease or replace the steering bearings, then get a 2010 YZF top seal – it is a much beefier design. FRONT NUMBER PLATE MOUNTING: The two studs on the lower triple clamp ('06 and up) that the front number plate mounts on can get worn. I know it sounds crazy, but those two studs can get serious notches worn into them from the front number plate vibrating around. Drill out the lower mounting holes in the number plate and install grommets. Aim for a tight fit on the studs to quell the vibration, thus eliminating any additional wear. WHEEL BEARING SPACERS: The spacers between the bearings in the wheels can compress over time. Frequent wheel removal & re-mounting and torque-ing speeds this up, and the spacer ends up being ‘short’. This subjects the bearings to higher loads, higher friction, and greater wear. Install new spacers if you have to replace wheel bearings. BRAKE DISCS: My rear disc was wasted – grooved, chewed, and blued – and the front had already been replaced once. Worn discs go through pads faster, so consider new discs if they look bad. FASTENERS: Every nut, bolt, and screw on this bike was tight, REAL tight. Like, I-hope-this-thing-doesn’t-break- “PING!” tight. Use Loc-Tite or some sort of never-seize on the fasteners. And don’t tighten 6mm screws with a ½”- drive ratchet! Gad! These bikes don’t vibrate THAT bad. Broken screws and stripped threads indicate poor mechanical skills. Don’t be that guy. You and your bike will be happier. SEAT: Yep, the seat! The ‘keyhole’ on the underside of the seat was worn oversized. Not a big thing, but the button on the tank had also been ‘sawed on’ by the seat, so those two things together allowed the seat to slide side-to-side too much. I bought a new button, then padded the end of the keyhole with a few strips of duct tape. This tightened things up nicely. REAR MASTER CYLINDER: Another crazy one, boots rubbing on the rear master cylinder can wear all the details off the aluminum body. Not a service issue, but it sure shows the bike has lots of time on it. FOOT PEGS: Many YZs came with cool titanium footpegs. A few early versions had pegs breaking, so be mindful of what year the bike is. Also, titanium wears faster than steel, so check for smooth, worn-down teeth. The footpeg pins can get worn as well, and that makes for a sloppy feel in the pegs, so consider refreshing those. FRONT AXLE: The right end of the front axle is a precision-machined cylinder, designed to be a nice smooth sliding fit into the lower right fork leg. There should never be a need to hammer on the axle, but if someone did, the smooth surface was most likely damaged and deformed -- ruining the slip fit into the fork -- and possibly introducing fork binding and misalignment. Use a flat file to remove any burrs or lumps on the cylinder that hammering may have caused. Ensure that the axle slides unfettered through the lower fork leg. Fork action will be smoother and bushings will last longer when the fork is allowed to align easily on the axle. REAR BRAKE CARRIER: The mount on the swingarm that engages the rear caliper carrier can get surprisingly worn down. This allows the carrier to flop around, accelerating the wear at the mount and the swingarm hole. The quick, cheap fix is to adjust the rear wheel so that the caliper carrier engages a less-worn area of the mount, chain slack permitting. I’m not sure of any other way to fix this, short of welding and machining, or buying a new carrier and swingarm. More?