Question for the dads kx 65.

I just purchased my boy a 2011 kx 65. We've come off KTM 65's. I was tired of the KTM, due to it nickel and dimed me to death, parts were hard to get in my area, so I got the kx, and my boy never rode it before, he was fast and aggressive on his KTM. So I figured no problem he'll be fine on the kx. We went to arenacross, and he had a hard time on the bike. Mind you the first time he rode it, had no practice time, threw him right into the race. I did have the suspension professionaly done he said it was nice. The problem is he had a hard time getting power out of the corners. The KTM had a powervalve, and had good low power. I realize the kx does not have the powervalve. I don't want go through the porting thing, just an easy fix, stock gearing is 13/47 do you think 48 or 49? And would a moose torque spacer work. I've heard 49 with the spacer is a good setup. The bike has pro circuit pipe and R304 silencer, v-force 3 reeds, just wanting to know if any body knew of any thing better. I won't do the washer trick, don't want to restrict it that much. Or does he just need more seat time? He's a very good rider, like I said. Maybe just needs to get used to the bike more. Maybe I haven't given him enough time to adapt. He's begging me to go back to KTM. I told him switching bikes all the time isn't the answer. Thanks for reading!!!