I think Funky Killer is asking how to make a race that works on the internet, not one of those buggy things that JJ2 uses (with Setlap and all).

Explanation on how to replicate a Setlap warp that's not all buggy.

Where the race ends, have a sucker tube, or a warp to the sucker tube.
In the sucker tube, make the player crash into a trigger scenery that vanishes from a trigger zone directly below the trigger scenery. Under the trigger zone should be a warp back to the start of the level. This will make it so the next time you come, you will go Through the trigger scenery.
Have as many cases of this as you want laps, though obviously wish different trigger IDs. After the last one, have a warp to the end area.