Actually, the split between the USSR and revisionist claims were before the Cultural Revolution. The split was over what the appropriate international policies of communist countries and internal politics of communist countries should look like. For China, the split started with two speeches given by Nikita Khrushchev at the Twentieth Congress of the Communist Party of the Soviet Union, in 1956. The first speech was the basis of the later disagreeements on communist policy, but it was the second "secret speech" that made the Chinese particularly angry. The Chinese Communist Party was not allowed to attend this secret speech, nor were they notified of it. The problems were also really related to politics, but more in the area of perception, I would say. For example, the attack on Stalin and his cult of personality was related to Mao Zedong, who also had cultivated a powerful cult of personality. If Stalin, the leader of communism, could be attacked, then what could happen to Mao in China? This had implications outside of China too. The Chinese thought this turn against Stalin was incredibly irresponsible, and they were proven right when later that year the Hungarian revolt happened and thousands of communists defected from their parties in the West. The CCP tried to preemptively fight this by giving an analysis of Stalin that concluded that his achievements far outweighed his terrible faults. This obviously failed.

Khrushchev's policies ended up being much more moderate than Mao and the CCP liked. He proclaimed that war between communism and imperialism was not inevitable and that peaceful transitions to socialism was possible. Obviously this was ridiculous to revolutionary communists. At first China went along with this, but by 1957, Mao had turned further left in domestic and foreign affairs, and this caused conflict between the CCP and the CPSU. The Soviets felt that Mao was trying to instigate a conflict between them and the Americans with his speeches and comments. At this point I am going to address "revisionism" specifically.

On April 22, 1960, the ninetieth anniversary of Lenin's birth, Mao launched four major polemics against revisionism, though without directly attacking the USSR. However, by 1963 this had turned into direct attacks on the USSR. From September to the following July in 1964, China issued nine polemics, which discussed their reasons for breaking with the CPSU. The revisionsism, then, would be the issues of Stalins, ideas about war and peace, peaceful coexistence, peaceful transitions to socialism, and the other examples of Khrushchev's revisionism. The last polemic was "On Khrushchev's Phoney Communism and Historical Lessons for the World", which ended up discussing one of the justifications for what became the Cultural Revolution. Elsewhere I have written on AH that the Cultural Revolution was in large part Mao's way of reclaiming total authority in the communist party after the Great Leap. However, this split also played some kind of role since in his eyes no revolution was on an island, and that his country's old slogan that "The Soviet Union's today is our tomorrow" was looking increasingly undesirable because of their revisions to communist doctrine.

I used Mao's Last Revolution by Roderick MacFarquhar and Michael Schoenhals as a guide when answering this question, specifically the introductory chapter.