[Frank Lee]

Honda has been running timing belts through the crankcase of small stationary engines for years.

LIFETIME TIMING BELT DESIGN
GC series, GS series
Honda’s GC and GS engines use the world’s first small engine internal timing belt, designed to last the lifetime of the engine.

Small engine timing belts are usually external and are subject to wear caused by dirt. Honda’s internal timing belt runs in oil, eliminating the need for conventional drive gears.

This design:

Improves lubrication,
Reduces the weight of the engine, and
Provides quieter operation.

http://engines.honda.com/why/technology