Suzuki DF25/DF30 Four Stroke Service Manual, Page 149Get this manual
7-32 POWER UNIT (3) Install valve guide to cylinder head Heat cylinder head to temperature of 80 100C (176 212F)Apply heat uniformly so that head will not be distorted Use special tools to drive new valve guide into holeDrive in new valve guide until special tool (valve guide installer attachment) contacts cylinder head After installing, check valve guide protrusion H