In a medium skillet, cook the bacon over medium heat just until crisp; drain on paper towels. When cool enough to handle, crumble the bacon and set aside.
Bring a large saucepan of salted water to a boil. Add the broccoli and blanch until bright green and slightly softened, about 3 minutes. Drain well, run under cold water to stop the cooking, and drain again.
In a mixing bowl, combine the mayonnaise, vinegar, onion, sugar, and raisins. Add the broccoli and toss to coat with the dressing. Refrigerate for 1 hour.
Just before serving, fold in the sunflower kernels and all but 2 tablespoons of the crumbled bacon. Sprinkle the reserved bacon over the salad to garnish. Serve immediately.