I recently acquired a new DSO203 (a.k.a. DS203) "pocket oscilloscope" from the evil auction site for less than $160 shipped (from the USA!). This was the least expensive model I could find with enough bandwidth-- 8MHz-- to do the ESC timing test. I wouldn't recommend this as a general-purpose oscilloscope, since the screen is very small, the voltage levels aren't very accurate, and the user interface is too cumbersome. But for this particular job it works pretty well.

The scope settings below are for the DSO203, but will be similar for other scopes. One problem with the DSO203 is that I have not found a way to tell it that its probes are on their 10X setting; when the scope says 0.2V/division, it's really at 2.0V/division with a 10X probe.

Set the scope probes to 10X.

Set channels A and B to DC coupling and 0.2V/division (which is actually 2V per division since the probes are set to 10X).

Turn off channels C and D.

Set the trigger for Auto mode, using channel A's rising edge, and the trigger threshhold to 200mV (which is actually 2V since the probe is set to 10X).

Set the vertical position for channels A and B so they can be easily seen; I put the channel A baseline at one major grid division above center, and the channel B baseline at one major division above the bottom of the screen.

Set the horizontal time base to 2us/division, and the horizontal position to a few divisions left of the screen center.

When you have made all of the above changes to the scope settings, save the settings so they are retained when the scope is turned off. Most scopes do this automatically, but the DSO203 requires a special effort (press the square key, use the left/right arrow switch to select "Save Param", then press down on the "+ -" key).

To do the test:

Make sure the power switch on the car is OFF.

Set the car on a stand so the tires can spin freely, and not tangle with any wires.

Remove the exisiting sensor cable and replace it with the test sensor cable.
Connect both scope ground (alligator) clips to the ground connection on the test sensor cable.

Connect the Channel A probe to the Sensor B connection on the test sensor cable.

Power up the transmitter and the car.

Connect the Channel B probe to the motor's C terminal.

Apply full throttle.

The sensor signal will be displayed on Channel A of the scope, and the motor drive on Channel B. The drive must change after the sensor change; this will be to the right of the sensor change on the oscilloscope screen, since time is displayed from left to right. If the motor drive changes before the sensor, that's timing advance (which is not allowed in "Blinky").

ROAR requires that the motor drive change no later than 10us after the sensor change. Some older ESCs have somewhat more delay than that, but in general they won't exceed 20 us or so.

When the test is complete, turn off the power on the car, remove the test sensor cable, and replace the original sensor cable.