Is there somebody locally that can help you out? Are your sure that you assembled everything properly? Also, make sure that you are adjusting the correct screw. One tightens the unit to the shaft, the other one is offset and adjusts the shift point. Make sure that you didn't loose the little ball that goes into the hole before the spring.
Here's how I start off adjusting. With the 2 speed disassembled, insert the ball, spring and adjustment stud into the correct clutch hole. Hold the clutch hole so that the finger rotates out of the housing. Now slowly tighten the adjustment untill the finger fully retracts into the housing. Give it another 1-1/2 to one full turn more tighter. Now assemble the 2 speed and install in the car. Start up the car and slowly rev it up. You should be able to hear and see it shift as you do this. If it doesn't, losten the adjusting screw 1/4 turn at a time, testing in between. Keep doing this untill you hear it shift. Once it does, you can fine tune the shift point to suit track conditions and gearing.