440 kit witch is best?

[handsomejon]

Got a new 03 400ex its bone stock and under powered,wanna do some hair scrambles & gncc.So I need it to still be reliable what do you guys think.Thanks

Jon

[s-10s_rule]

Oh god this is gonna get ugly I can see it already....
Look at all the posts about engine builders, everyone loves TC racing, GT Thunder, Sparks Racing, or C&D Racing. All of them are supposed to be baddass

[3x440ex]

i would go with the 416.....i've owned both 440 and 416 motors and the 416 pull just as hard if not even harder than the 440.....the 440 is gonna cost alot more if you have it done right. like a couple grand more....you can build a nice 416 for under $500

Ross 416 piston from C&D..... $130
gaskits......................................$45
Hot cam..................................$120
HMF slip on.............................$200

That's it.....you don't need the full exhaust or head porting, you won't see big gains from these mods with this motor. you might want to buy a carb $420

[TC426EX]

440's rev slower, heat up faster, and are less reliable than a 426 or 416 and the power gains from the extra cc's is minimal at best. Get your cylinder bored to accept an 88mm piston (426). You can have this bore performed on the stock sleeve where if you did a 440 you would have to have ths cylinder re-sleeved after you bored it. If you have the money to spend, I would go with a kit from a reputable engine builder. There are alot of hack job garage done 440's especially with that IMS kit that turn out to be real dogs even thought they are "440's" and all man... The larger piston is not gonna do much without a cam, and an aggressive port job DOES help out. IF you are gonna be racing harescrambles, I would reccomend the TC 926 grind XC cam for you youll love it. Youll want a High rev CDI unit from TC racing or GT thunder as well to give you the top end revs to be competitive. As I always suggest, you will want to go with a heavy duty head stud kit, or heli-coil your existing ones to prevent from blowing head gaskets. Most EX's that have built motors with compression added have a tendency to blow head gaskets. Even if you go with one of the smaller bores like the 416 I would STILL reccomend hooking up your head studs one way or another. Its a pain in the *** to build your motor, get it together and then blow a head gasket and have to fiddle with valve adjustments and all that all over again trust me. Get a carb eventually, but until then, have the choke removed from your stock carb and jet it accordingly. This will give you a better fuel/air flow and will make a difference. You will also want a full exhaust system like a sparks or HMF or something to help with the added exhaust volume your motor will produce.

If you have the money I suggest the following...

-426 bore with high compression piston (over 11:1 compression if you dont mind using race gas)
-TC 926 XC cam
-Port + Polish
-heavy duty head studs (or heli coil yours to save $$$)
-Full exhaust (Sparks or HMF)
-remove choke from your stock carb
-TC Racing or GT Thunder CDI unit

With these mods you will have a whole new bike ready to set the woods on fire!!