Baggage allowance:

International Travel - between North America and Asia
Coach Class: Each ticketed passenger is allowed two (2) pieces of checked luggage.
Each piece: 50 pounds (23 kg) with linear dimensions not to exceed 62 inches (158 cm).
Checked luggage within the free 2 bag allowance that weigh more than 50 pounds and up to 70 pounds will be assessed a $50.00 heavy bag fee.
Checked luggage within the free 2 bag allowance whose linear dimensions exceed 62 inches will be assessed 2 excess baggage charges.
Checked luggage within the free 2 bag allowance whose weight exceeds 70 pounds will be assessed 3 excess baggage charges.

http://www.nwa.com/travel/luggage/checked.html