Be cautious: Many online PDFs are for the Honda CG125 or CB125. While similar, there are critical differences in clutch assembly, CDI timing maps, and bolt thread pitches (JIS vs. metric). For the 152FMH specifically:

The "IN" mark stamped on the piston crown must face the intake valve (top). Torque Specifications

Check every ride; change every 300–500 miles (or 15–20 hours of off-road use). Valve Clearance: Inspect every 1,000 miles.

The timing chain, or cam chain, synchronizes the crankshaft and camshaft. A loose or worn chain can cause timing issues. Proper alignment of the timing marks is critical when the chain or associated components are replaced. The procedure involves:

The pilot jet inside the carburetor is clogged with varnish or debris. Remove the carburetor bowl and clean the jet holes with compressed air and fine copper wire.

Clogged pilot jets are the primary cause of poor off-idle throttle response. Remove the carburetor bowl and blow compressed air through the microscopic center hole of the pilot jet.

Most owners ignore the 152FMH until it seizes. A proper service manual outlines a brutal but necessary schedule.