I was thinking about modding my 400ex a little bit, I was wondering how much I could pick up with a stage 2 hotcam, k&n air filter, jet kit, and a pipe. What would be my chances of keeping up with maybe the 450's, raptors, z 400's etc. Could this help my ex outrun any of these quads in a drag race or top end? Or should I just forget about it and not spend the money on the parts. Thanks for any input

 

Personaly, i think if you are goin to have the top end torn down, you might as well put the 440 kit in while you are at it. I did that to mine about a year ago, and loved it. as far as keeping up with the 450s, and raptors, you won't. I could beat a piped and jetted Z. Before all my mods he was beating me all around. I just sold mine and bought a 450er. and i kill the 440. Mine also ran very hot when riding real slow first gear trails in the woods. it all depends on what kind of riding you do. even with the 440 kit the motor was still reliable.

 

I would keep it stock and save for a 450. You will end up nickle and diming it and wishing you had more power most likely. 440 kits on 400ex's have the tendency of blowing head gaskets out. Just my 2 cents.

 

Keep it stock and it will last forever... I ride with friends that have Raptors and keep up with no problem. It is very rare that we line and drag race....

 

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HEY MAN UMM I JUST PUT A 440 KIT ON MY 400EX AND I HAVE A BIG GUN RACE SERIES PIPE WITH K&N WITH AIR LID OFF AND SNORKEL AND THE RIGHT JETS AND I LINED UP WITH A 450 HONDA N I HAD HIM THROUGH ALL THE GEARS THEN HE BERALLY STARTED TO CREPPING UP IN ME BUT THERE WAS NO WAY HE WAAS GUNNA BEAT ME BUT RAPTORS THERE NO MATCH AND Z 400 FOR GET ABOUT IT I SAY ITS ALL IN THE DRIVER (SHIFT RIGHT) AND YOU GOT IT. ANY QUESTION REPLAY
PEACR

 

You will need lots of $ to keep up with 450. the mods you are talking about will livin it up maybe go with a higher compression piston also with what you want to do. I love riding my 400ex only bolt on mods. yes it is under powered I ride with z400 trx450 raptors. cant beet them in a race but have lots of fun riding with them

 

I have had 2 EX's now. I have ridden the TRX 450 which is hot and I have cousins and buddies that all have Raptor 660's which don't have near the ride or handling that the EX has. Mind you the 700R is alot better but if your drag racing then buy a street bike, if your in the mountains or the sand dunes then it is all the rider cause they all have to try to keep up with me most of the time. I wouldn't put the 440 kit on it I would keep it stock but you can never go wrong with a pipe and a K&N filter in fact it is much healthier for your engine. I have a FMF Fatty pipe and I love it. You can also just remove the baffle from your factory pipe which helps and depending on how much water you are into, I drilled 4 holes about an inch wide in the top of my airbox under the seat and I noticed immediate throttle response. Don't bore out your engine unless it blows on you. Just my opinion.

 

Putting mods on your 400 will help you get to your top speed faster but if you want to keep up with the faster atv's then you need to change your gearing, i have a 36T sprocket on the rear of my 400EX and i will keep up with most of the z400's if not beat them, raptors pull away but with the right gearing and the right mods to the motor you will have top speed and the power to pull u through the gears faster. I found out that with changing the sprockets and not adding big upgrades to the motor you will lose a lot of bottom end, but if your about going fast on top end all the time, change the sprockets

 

My buddy has a 400EX whit the 440 kit in it with 13.5:1 compression, a stage 2 Hotcam, HMF pipe, Big gun rev box, and a few other goodies. He could keep up with my 450R when it was bone stock. Now with a few mods on my R he can't even come close. Save your money and buy the 450R and mod it.

 

If you go to a 440 kit, you might consider working with Mickey Dunlap at Four Stroke Tech. He seems to have a handle from problems with blown head gaskets.

/jon