In California, there is generally no mandatory 15-day waiting period when purchasing a new motorcycle. Once you complete the necessary paperwork, pay the required fees, and register the vehicle, you should be able to take possession of the motorcycle immediately.
It's best to check with the specific dealership where you plan to make the purchase to understand any possible waiting periods they may have.
Regarding insurance, California law requires all registered vehicles, including motorcycles, to have liability insurance coverage. This means that before you can legally operate the motorcycle on public roads, you must provide proof of insurance or an alternative form of financial responsibility.
While insurance is required by law, it is not necessary for the motorcycle to have insurance in order for it to leave the dealership lot. However, it's highly recommended to have insurance coverage in place before riding the motorcycle on public roads to protect yourself, others, and your investment in case of accidents or damages.