Light your grill to medium high, direct heat.
Drain and throughly rinse the black beans, allow to drain well (we don't want all of that water to dilute our mix!).
Mince your jalapeño. For less heat, remove the seeds and white flesh (but don't be a wuss).
Once the grill has preheated, grill the shucked corn over medium high heat for about 4 - 5 minutes.
Open the lid and roll the corn a quarter of a turn, close the lid and keep grilling for another 4 - 5 minutes.
Repeat the rolling and grilling operation until the corn is tender and you have some charring (not too much) on all sides of the corn cobs, it should look like this:
Remove the grilled corn and allow to cool.
Using a sharp knife, cut the grilled corn off of the cobs.
In a large bowl, combine all ingredients and stir, adding salt and pepper (and more cumin if you like) to taste.
Cover the bowl and refrigerate for about 30 minutes to let the flavors become friends. Stir, taste, add more salt and pepper and/or cumin to taste.
Serve cold or room temperature.