Combine mustard, sesame oil, garlic, pepper, and maple syrup. Place pork in a shallow dish and coat thoroughly with marinade. Cover, then chill in the refrigerator at least eight hours, or overnight.

Preheat grill for medium-low heat.

Remove pork from marinade, and set aside. Transfer remaining marinade to a small saucepan, and cook on the stove over medium-low heat for 5 minutes.

Brush grate with oil, and place meat on grate. Grill pork, basting with reserved marinade, for approximately 15 to 25 minutes, or until interior is no longer pink. Avoid using high temperatures as marinade will burn.