During the second half of the 1960’s, the Csepel Motorcycle Factory made important progress in engine noise reduction.

Following foreign standards, national noise levels became obligatory, and domestic production adopted new standards.Under these circumstances ever-higher demands were placed upon development, to dramatically reduce exhaust noise levels, while maintaining important internal pressures required for two-stroke design.
With the introduction of the „suction noise-reducer”, the T5 (and other models) adopted the letter H (Halk = silent), to denote the new component.