I am considering a gearing change on my 400 to give it a little more low end for the trails and hopefully make it easier to loft the front end. Either going to a 15/47, 15/48, or a 14/45. I figure with the 14/45 I should be able to reuse the stock chain, but what about the other two combo's, will they require longer chains?

I know you are supposed to get new chains and sprockets at teh same time, but this is a very low mileage bike with no wear showing on the sprockets or chain.

15/45 or 14/45 will work with the stock chain length (108 links). 15/47 or 15/48 will need 2 more links (110 links). I run 14/48 with 110 links.

Try the 14/45 combo. It should give you what your looking for. It is cheep/easy to change & gives you the option to switch between the two. Hope this helps.