A speeder bike keeps moving for a little while after you jump off. If you time it right, you can jump off with the right distance for the bike's mines to move out of your range and into the enemy's. I've done it before, but its not something I do very often (maybe twice).
I'm not sure about having a time bomb. A mine goes off if an enemy is within range of it. The time bomb, would have to be more powerful than a mine, or you would have to explode it when the enemy is just as close to it as a mine, inorder to kill the player. However, I have never used a time bomb in any games that I've played, so I don't know many tactics for it.