You deff need a 14 up front, your bike is modded purrfect to go up a sprocket with 20's
You said he wants to blow it...
I think That tells us lots.
I get the feeling you are not in a hurry to blow yours...
I drive mine like I stole it.
Balls to the wall every time all the time
and I win
Every time. I spank the pants off dirt bikes and quads and after I win every one of them says "Well, I didn't want to blow it".
I could care less if I blow the motor because I have other ones I want to put in it. So if you want to win, you have to push it! learn your bikes limits, listen to it feel what it is doing and become one with the bike, have no fear and get some good brakes and don't let off till after he does if it's close.
How's your bearings and stuff is there any drag when you push it in neutral?
haha there's always the chance he modded the sh*t outta his and he won't tell you. That's something I would do for giggles.
Bottom line is get a 14 up front, and give her all she's got! Just remember to hang on!