The 1988 Yamaha YZ 125 received several updates that kept the bike modern.

Power: The '88 Yamaha engine made generous quantities of low-end power and delivered very authoritative mid-range RPM power! The engine did not produce much top-end power. This engine power required the rider to shift like crazy in sand or in soft, deep corners when racing.

Suspension: The TCV forks from '87 were ditched in favor of cartridge forks that performed admirably in all terrain. The rear shock received some minor changes, but it was harsh over square edged bumps without revalving. Yamaha ditched the BASS system, finally.

Handling: The YZ was a stable bike at speed and most folks felt the YZ was a very comfortable riding machine. Additionally, the bike could carve pretty sharp turns too.

Reliability: The '88 YZ was reliable.

Odds & Ends: The YZ came with a front and rear disc brake. The BASS did not appear on this bike, nor did it ever appear on any YZ again. Do not believe for a minute that there was something wrong with the '88 YZ 125 transmission. It was intentionally borrowed from the '87 YZ 125 and then re-designed to shift terrible again in 1988. The '88 YZ will make a good play/trail bike if the rider can handle the mid-range power wallop.

Other notable design updates:
Clutch contained one extra set of clutch plates
Larger diameter front disc