Place lamb in a large bowl; set aside.
In a small pan, stir together vinegar, jam, curry powder, sugar, chiles, onions, garlic, and bay leaves.
Bring to a boil over high heat, then remove from heat and let cool.
Pour vinegar mixture through a strainer over meat in bowl; discard residue.
Stir meat to coat.
Cover and refrigerate for at least 4 hours or until next day, stirring several times.
Lift meat from marinade and drain briefly (reserve marinade).
Thread meat equally on about 10 sturdy metal skewers.
Place skewers on a lightly greased grill 4 to 6 inches above a solid bed of medium coals.
Cook, turning often and basting with marinade, until meat is well browned on outside but still pink in center; cut to test (10 to 15 minutes).