what area are you in. Lots of grass fields in indiana. The field ridind takes a way different setup than sand. You dont need any more top end you need to make it hook and have a controllable powerband. The 13 tooth is a better choice than the stock 14. The 12 might be even better for what you are doing but like someone else said they wear out quick. I recommend the 13 tooth with a 41 tooth rear sprocket. That will get you into 6th alot quicker. The lower gearing is funny in the grass it will make it easier to spin the tires but makes the spin more controllable and lets you get it back up on the pipe quicker after backing off. very important in grass/ field riding Might as well get a chain while you are getting new sprockets. Def do the timing plate it is inexpensive and more timing will give you better low end. My next mod recommendations would be Getting your stock head milled or a coolhead to raise compression. Then pod air filters. and a good radial tire like what comes on the 400ex, or the raptor, and the yzf 450s. Those type of tires hook the best in the grass. IMO Then the only thing left is a cheap set of used pipes like FMFs hope that helps