Srila Prabhupada Japa 16 Rounds 1728x Hare Krishna Maha Mantra.

Sankirtana yajna is the proper yajna for the Kali−yuga:

When learned sages and brahmanas assemble to chant Vedic mantras, some of them also engage in arguing about the conclusion of the scriptures. Thus some of the sages and brahmanas were arguing, and some of them were chanting the Vedic mantras, so the entire atmosphere was surcharged with transcendental sound vibration. This transcendental sound vibration has been simplified in the transcendental vibration 

hare krsna hare krsna krsna krsna hare hare
hare rama hare rama rama rama hare hare

In this age, no one is expected to be highly educated in the Vedic ways of understanding because people are very slow, lazy and unfortunate. Therefore Lord Caitanya has recommended the sound vibration Hare Krsna, and in the Srimad Bhagavatam (11.5.32) it is also recommended: yajnaih sankirtana−prayair yajanti hi sumedhasah. At the present moment it is impossible to gather sacrificial necessities because of the poverty of the population and their lack of knowledge in Vedic mantras. Therefore for this age it is recommended that  people gather together and chant the Hare Krsna mantra to satisfy the Supreme Personality of Godhead, who is accompanied by His associates. Indirectly this indicates Lord Caitanya, who is accompanied by His associates Nityananda, Advaita and others. That is the process of performing yajna in this age.

– Srimad Bhagavatam 4.4.6

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