13/51!
How in the world do you keep the front end on the ground?? I race some of the National Enduro races as well as the ISDE Qualifiers, and can be some of the most technical riding known to man. The lowest gearing I run is 14/47. I tried 14/49 last year at one day of a Qualifier, and could barely keep the front end down. Hated the whole day.
Also, about a month ago, I spent 4 days in Moab, Utah (rock crawling, Jeep heaven), where you almost never get into 2nd gear, and the 14/47 was more than sufficient to walk up all stair step rocks. More like trials riding a KX500 than anything else.
One note, I started running a flywheel about two months ago, and boy did it make a difference in the tight stuff. I would suggest a 14 oz. flywheel with the stock gearing before spending a lot of money of new sprockets. I think you will be surprised.
Rick