To get the jump needed to jump the gauge, go to the truck full of fertilizer, loosen the wheels with the tire iron, and then push the truck over. Once you have done this, pick up a handfull of fertilizer and go to the old mine road, throw this in the eyes of the man with the chainsaw- this will gain you the chainsaw which is used to knock off the guy with the big plank of wood. Use this plank of wood to knock off the cavefish, which will gain you their special goggles which you use on the mine road to find the cave. When in the cave attach the jump to your bike and drive off till you reach the bend in the road, unattatch the jump from your bike- which pulls off the reflectors in the middle of the road- this makes the cavefish crash. Once you've completed all this go to the gauge and JUMP!