My grandson at first wanted a dirt bike cake but changed is mind and wanted a dirt bike volcano exploding cake.  My daughter found the little lego guys for the cake.  I made this a two tier cake, the volcano being the second tier has support under it.  The lava was made with candy melts on toothpicks.  I piped the lava in different shapes with toothpicks on one end which were inserted in the top of the volcano.  The cake was a hit and when we pulled all of the toothpicks out of the top of the volcano before cutting the cake, the kids all had to taste the lava and came back for more.