Super Mario Bros. (NES) - Timer Glitch

[ColecoFan1981]

For players of Super Mario Bros. (NES) and Super Mario Bros. 2 (Japan) (FDS): Has anyone been able to execute the timer glitch wherein you try to get Mario (or Luigi) to touch the flagpole the instant the timer reaches 000 (at which point you normally die)? If successful, the timer will count down all the way from 999 ticks, giving you a total of 50,000 points to your score.

I've heard people say this glitch can be done on Super Mario All-Stars (SNES) versions of SMB and SMB2J at the end of all castle levels (when you touch the axe as the timer reads 000), but I wonder why it doesn't work the same for the non-castle levels (meaning no points at all when you touch the flagpole)?

What would the instructions be to make the timer think it's counting down from 1000 ticks? A Game Genie code would probably help for the non castle levels.

~Ben