Jerry asked me to give details on the air shifter operation on my bike so those unfamiliar can understand the reason we use them in drag racing. He also wanted to me give information about why we “spot” at the starting line.
In regards to the air shifter, there are several reasons why we install the system on a dragbike:
1) Primarily it lowers the ET because the rider no longer has to physically shift the bike, with the exception of a press of a button. The only movement of the shift lever is by mechanical means via a pneumatic cylinder.
2) The rider is able to make full throttle, clutchless shifts by the press of a button. This is possible because the ignition is momentarily interrupted, just long enough to unload the transmission which allows the transmission to shift easily to the next gear. If a bike was manually shifted, there is a delay between shifts that briefly stops full power, forward momentum. This affects ET due to lost time in moving the bike down track. As much as a tenth to a tenth and a half second can be dropped from your ET with an air shifter.
3) A typical air shifter used on bikes today utilize an electric over air system. That is, the shift components are a combination of both air, and electric. The system consists of a 12 volt, momentary button to activate the components. Power goes into the button from a main power switch. With a basic system using a Dyna S ignition, when the button is pressed, voltage goes out to activate an electric over air solenoid. Air to the solenoid is supplied by an onboard tank pressurized at a minimum of 120PSI. On the outlet side of the solenoid, a “T” fitting is installed and the air lines are run to a pneumatic valve with a microswitch connected on top. This switch has a 3 terminals- a common (input), a normally closed and a normally open. In the case of a Dyna S, you would route the main power supply wire for the ignition to the common terminal, you would then connect the wire going to the ignition plate itself to the normally closed terminal. The idea here is when you press the electric button, the electric over air solenoid will send air to the pneumatic valve and the plunger inside will push against the microswitch breaking contact to the normally closed terminal. This will momentarily drop power to the Dyna S and the engine will “kill” for a split second. Now in order for the transmission to shift, the “T” connection mentioned above has an air line that runs to the pneumatic shift cylinder connected to the shift lever. Both the engine “kill” function and the movement of the pneumatic cylinder/lever must happen very close to the same time in order for the bike to shift. Theoretically, you want the engine to kill a split second before the bike tries to shift so the transmission is fully unloaded. You alter this differential in time by lengthening the air line to the shift cylinder by approximately 6” longer than the one to the microswitch “engine kill” assembly. Through this whole process, the rider never touches the clutch lever or rolls out of the throttle.
In the case of my bike, it has an electronic ignition controller with an internal engine kill function. Therefore, it doesn't have the external pneumatic microswitch engine "kill". It does have the electric over air solenoid that activates the shift cylinder connected to the shifter lever. I can alter my "kill" time by programming it according to my needs.
Spotting:
As to the “spot” technique, when watch the video you see my wife kneeling with her hand on the track at the starting line. The “spotter” is responsible for assuring that a location is found on the track to give the best traction. This is called the groove. Its normally where the most traction can be found. Sometimes the “groove” may not feel sticky and adjustments to the left or right have to be made so the bike can hook up off the starting line. The spotter is also looking for fluids, debris or anything else on the track that can contribute to problems off the launch. Race officials sometimes don’t catch the little things and it can lead to disaster for the rider. It may not seem to be an important task, but a good spotter on your crew can save a life and your bike.
I'm not an expert on any of this, but i hope this might clarify the items that Jerry wanted me to address.
