can a 440ex keep up with the new 450s if not how close is it and also how much horsepower would i gain from a 440 big bore kit this is what is included in the bigbore kit Namura 440cc Big Bore Piston, Rings, Circlips, Pin, 440cc Hi-Performance Gaskets, Advanced 440cc Sleeve, Magnum Hi-Performance Rev-Box, Magnum Stg. Performance cam. I also have white bros pipe and uni airfilter with no airbox lid and im also getting the white bros header pipe soon and a new wiseco crank and new UM airbox with all that would i be able to stay with 450s

 

Ok, I know I am going to get flammed for this but I will give you my 2 cents. I built up a 2003 400ex to try and keep up with the 450's. (I ride the dunes of So Cal).
Put in a 426 88mm piston, and a hot cam. Already had a Duncan Fatboy pipe, jetted and a K&N. I know there are many more mods that can be done, just got to costly.
Yes it hauled A$$. But not like the 450's. Bike ran real hot. Had to always stop to let it cool down. Then the old argument of race gas or pump gas. Just became to iffy. Well I sold it today for $4000. Said screw it and will buy a liquid cooled 450. You did not mention what type of riding you will be doing and I know you asked about a 440 kit, not a 426. Just does not seem worth trying to make apples out of oranges.
Have fun with your bike or get a different one.
Peace and Happy Holidays.

 

put enough money into it and it will keep up with anything. but remember, it won't be a 400EX anymore, and reliability will suffer, guarranteed.

 

Some say that the 416 is better, I don't have a clue but it will be hard to keep up with the 450's. But I have seen soem alky EX's beating them.

 

my riding bud spent near $2500 in motor work on his 440 and he lost everytime to his brothers stock yfz450.

 

that cant be true because before i put my 440 in i raced my friends yfz(see pics) and only lost by about 3 quad lengths in a drag where u reached top 4thgear... with his bike still stock i can pull him from 1-3 by about 2 lengths then in 4th he starts to gain but its about even by the end of the race... mayb ur friends 440 wasnt made good

 

My cousin has a 440 and raced my yfz in 1/8 mile and lost by five bikes and he also has about $2500 in it

 

wow that sucks! lol

 

I have a 4mm stroked, 87mm piston 440ex. I have a web cam in it. It will not compete with my barely modified 450r. The 440 is apart right now for an 88mm that will make it 450, or 451 and It still won't run the 450r. I wish it wasn't true but it is.[img]i/expressions/face-icon-small-sad.gif[/img]

 

Well it's said, the 440 can't keep up with the new 450's. But still I have seen some alky beat them.