Suzuki Uz125 Service Manual ((link)) Guide

Warm up the engine for a few minutes, then remove the drain bolt located at the bottom of the engine. Replace the washer if it appears crushed and refill with 700 ml of 10W-30 oil.

The plug is accessible via the maintenance cover under the seat. Ensure the gap is set to 0.8–0.9 mm using a feeler gauge. Suzuki Uz125 Service Manual