IMO, you're wise to revert to a 13T on the front because of the reduced risk of the chain destroying your swingarm. A 47T will yield slightly shorter gearing and your chain length will only require 110 links.
Changing one tooth up front is roughly equivalent to 3 teeth in the rear.
The stock combo 13/43 has a ratio of 3.31
12/43 = 3.58
13/47 = 3.62
13/46 = 3.53
Good reference here:
Originally Posted by ecarnell
Anyone run a dirt tricks sprocket 13/47 combo on their WR?
I've asked on the wr250r forum, but only one reply.
In need of a new chain and sprocket after 12,000km of hard running.
Currently Using a 12T front and sprocket 43 rear - and like this gearing so want to keep this ratio - but back to a 13t front.
Thinking of the F1 13T front, and a YZ47 Rear - and a new Regaina ORN6 O-ring chain (520X120 Links).
Any reason why this wont work (besides new counter sunk bolts required)?