It should be stamped on one of the sides, Or simply count it.
The front sprocket has 14 teeth. the rear has 41 teeth, but on mine i have 13 front and 42 rear its more bottom end performance
The chain is size 530, and the stock gearing is 15/45, meaning that the front sprocket has 15 teeth and the rear sprocket has 45 teeth.
16 teeth in the front 45 teeth in the rear
They came stock with a 49T or 48T rear sprocket you can choose a replacement with either a 48T, 49T, 50T, or 51T, if you have the old sprocket count the teeth on the sprocket and that tells if it is a 48T, 49T or whatever (48T = 48 teeth)
For the '06 - 48 teeth in the rear. 13 in the front. For the '07 - 49 rear. 13 front. Not sure about '05 or '08.
on an 2005 trx450r there are 12 teeth on the front sprockeet and 37 in the rear
depends if the sprocket is bigger or smaller than a stock sprocket.
13t front 40t rear
The chainring by the pedals and the sprocket(s) by the rear wheel.
45 tooth rear
12 counter sprocket 47 rear
I run a stock rear sprocket and 15 front. does great for 500 ft drags