What's wrong with Yamaha speedboat's reversing jitter?

The reasons for the reversing jitter of Yamaha speedboat are as follows:

1, the spark plug is not working well;

2. The vacuum tube leaks;

3. Abnormal throttle opening. Yamaha is the world's top brand of motorcycle ATV. In the United States, the world's largest ATV market, Yamaha's sales are second only to Polaris. Yamaha has been committed to manufacturing world-class leisure sports products.