what is the maximum allowable luggage weight for a jal flight to narita and how pieces are allowed?

Answer 1

You didn't say from where. For flights to/from the US, airlines allow up to two pieces of checked baggage at up to 70 lbs each at no charge. Above that number and weight, the airlines will charge a fee. Typically they will disallow any bag above 100 lbs. Domestically, each airline sets their own limits as to number and weight.

Answer 2

Check with the airline, each airlines regulations regarding checked luggage is slightly different.