Mysql full text seach not working for 2 or 3 characters -

i created fulltext seach index , set ft_max_word_len=1.

when do:

select * tablename  match (title,description,content) against ('ニ')  order tablename.start_time limit 50

or when do:

select * tablename match (title,description,content)  against ('ニュース') order tablename.start_time limit 50

it show 50 record.

but when do:

 select * tablename match (title,description,content)   against ('ニュ') order tablename.start_time limit 50

or when do:

select * tablename match (title,description,content)  against ('ニュー') order tablename.start_time limit 50

it shows empty result.

can explain why?

Script