Here are a couple of things to pay attention to when you start looking at YZs. Check the front pipe mount under the water pump. The mounts have a bad habit of breaking in half and allowing the front of the pipe to sway back and forth on the end of the cylinder. This movement will wear the cylinder out in a hurry. If the mount is broken, it’s probably been like that for a while. The pipe seals on the cylinder with two O rings. If the front of the cylinder is worn, there’s a good chance the engine has been sucking dirt. Another thing to check is the joint where the air box meets the boot. They have a tendency of coming apart after a couple of crashes. A bent sub frame is usually the cause. The transmissions on the bikes are great when they’re new but have some serious design flaws. The forks and rods are one in the same and can wear the bores in the case out. This in turn leads to a misalignment of the forks and the gears causing premature gear failure. So far this year, I’ve rebuilt 4 YZ engines newer than 2011 and all of them had transmission problems. When the owner starts the bike, listen for a clicking sound that speeds up when the engine is wound up in neutral. This is the first sound you’ll hear when things are starting to go bad. Listen for the same sound when you put it in gear. If you hear it, walk away or get ready to drop $600 on transmission parts.
