As previously previously mentioned 99% of the time an engine starts backwards from overpriming. The trick of course is just to start gradually reducing the amount you prime until you hit the sweet spot. Or use the brute force method of an electric starter but then you'll never find out exactly what the engine likes. The reverse flick method is simply taking advantage of an overprime, slight as it may be.

The remaining 1% of the time is by using a power panel and overheating the plug which makes the engine fire too early.