Power: The '90 Yamaha engine received a larger carburetor and revised power valve that gave the YZ a mellower low-end thrust but a massive, yet smooth, mid-range punch. The YZ engine delivered usable and relatively strong top-end power. This was rather uncharacteristic for a Yamaha.

Suspension: The YZ 125 was delivered with upside down forks that were too sprung soft. After installing firmer springs, the YZ forks worked extremely well on everything. The rear shock received some minor changes, but it felt very stiff on small bumps. The rear would absorb any large bump at speed very smoothly. It skated around on small choppy bumps, unless the pilot was riding like a banshee with fire ants in his or her shorts.

Handling: The YZ was a stable bike at speed and was very capable of turning sharply. The machines layout was flat and comfortable. Its midsection was a tad wide.

Reliability: The '90 YZ 125 was a reliable bike.

Odds & Ends: The '90 YZ will make a good play/trail bike if the rider can handle the mid-range power punch. A few of these bikes are still being raced today.