Hi. im 12 and have a 2003 xr100r and am getting big for it. a 150r is too expensive, and i'm looking to ride in the sand. I was thinking about an 85 2stroke, but my brother says im a little bit small for an 85 and should just get mods and upgrades for it for now. I don't want to buy a big-bore kit, and I was thinking about a powercore 4 by fmf, and a bigger rear sprocket to hold me off for now. what should i do?