Where do you feel the power addition was in the rpm range?

Does it pull more on top or bottom etc?

Reason I ask is that I understand the powerbomb header is supposed to allow normal gains thru the mid to top, but without robbing much from the bottom (due to the powerbomb chamber etc)

 

Are the Big Gun systems pretty good for the 400ex? Buddies has one...I've been thinking about getting one also. I want to hotcam mine also. Wonder what kind of power gain I can expect from that.

Hey reconranger your over on TT to correct? Has to be you...don't see to many people with that same line-up of bikes.

 

I use to have a 02 400ex and did some mods to it. If you are going to do more than a $1000 in mods then why not just sell it and get a 450. I just don't think it is worth buying a 400ex then putting all that money into it why not just buy a raptor 700 or 450R or something like that if you are going to spend that kinda money in the long run. Because after you do any internal work in the engine you have defeated the purpose of buying a 400ex which is it's dependablity. I love the 400ex don't get me wrong I say just put a silencer on it rejet it a new filter and do regular maintanance on it and have fun with the bike. The shocks are great for the power the bike provides it you are not doing like triples with it. When I had my bike I wanted to do so many things to it but after I figured how much it would take to make it even come close to a raptor or the 450's it just wasn't worth it. Just ride it and have fun with it and don't try to compete with it. That's what they make the 450's for and other faster bikes. I don't want to sound negative but I have been thru it and realized that I wasn't having fun with the bike cause I was always wanting to be faster or working on the bike to make it faster when I should have just bought something that was faster to begin with. And there is always someone faster than you. Just my opinion.

 

I don't have much $$ invested in my 400ex so I plan to mod it some. I don't race it or anything so it doesn't need to be faster than a 450. I just like tinkering with stuff. Modding stuff is half the fun for me.

Buddy just got a 660 raptor. Its nice but it isn't that impressive. Another buddy outruns him on his 05' KFX400 everytime. Raptor complains about traction but no matter who rides them its the same outcome.

KFX700 beats then both by a couple quad lengths easy. Hard to outshift an auto [img]i/expressions/face-icon-small-wink.gif[/img]

 

I agree with you AR15guy I do like tinkering with stuff too that's why I got a old 300 kingquad to restore it was fun and now I am having fun riding it. I had a 02 660 Raptor and I had raced a Bruteforce and it kept up with me pretty good. I could see a kfx700 giving a 660 raptor hell but a KFX400 should not be out running a 660 raptor at all. Now a polaris preditor gave me hell I must say and a z400 is a fast bike also but not as fast as a 660 raptor if the driver knows how to keep the front end down on a raptor. Well I hope you have fun modding your bike. Remember fun is the reason why you got the bike. I think along the way for me I forgot about that and it almost stop being fun for me but an obsession.

 

Thats a good point (maybe except for the raptor since its very different from the other two) and for what you gain in the model change to the 450r from the 400ex its deffinately worth considering. If you already own the 400 then you have to consider your loss from selling and the added cost of buying a more expensive machine too, and I dont believe any atv is completely ready or right in stock form so expect on spending some more cash on the 450 after you own it.

I understand your take on the stock suspension vs the stock speed (and not too many of us doing trips anyhow lol) but if you ever get to ride one with a full aftermarket suspension that is set up right you wont believe the difference.

And for those of us who had updated or modded our 400's before the yfz or 450r were out we are in a totally different situation because there really wasnt any valid choices beyond the then questionable z400 (remember the frame issues etc) or the Cannondale as all the others at that time were just not on the same level and either had handling or other issues that didnt make them a good choice except for straight line acceleration.

Point is your in a different situation if you had already put enough $$$ and time into it that you not only cant get out without a large loss, but also are not all that much apart from the performance of the others.

Still I see a 450r in my future as well, and when you consider all the advantages in the long run its well worth it. Even just the benefit of liquid cooling is worth it to anyone interested in creating more hp (heat) as it eliminates the largest problem I have had with the 400.

And then there are those who just ended up with the 400ex for whatever reason and just cant afford to make the swap, but still are able to add on the mods one at a time etc.

Like I had said earlier the way to go for the best bang for the buck is basic intake and exhaust mods, and then onto suspension (front shocks, rear revalve etc or more). These alone will make the largest difference, and its a very noticable difference at that, and also without the larger expense of the new purchase or all the other mods that dont produce as much as noticable a difference for the $$$.

 

440ex026 I agree. Before all the 450's came out it was hard not to upgrade the 400 class machines to make them faster. And even now as long as you are not trying to compete against the 450's with a 400 class machine you should be ok. Really it's all about how bike your pocket book is and how fast you want to go.

 

The Z400's only have 5 less HP than the raptors. The raptor will beat it top speed eventually. But up until top speed I watch the kfx400 win everytime. Rider on the raptor is a better/ more experienced rider also.

The kfx400 was bought new and the rappy was recently bought used so its hard to tell what its history is.

 

ya all that stuiff will help A LOT but tires will also help a good deal

 

I just picked up a used 2005 400ex and have started some mods. It came with a Yoshimura mid pipe and muffler. I leave the spark arrestor in for slow trail riding and hill climbing and take it out for faster trails and drag/flat track riding. ITP aluminum mag rims with Holeshot XCR tires and a K&N Air filter were also installed when I bought it. Since I've had it I've done some changes. Added 5 inches to rear width and 3 inches to front width with Dura Blue spacers. Changed front sprocket to a 15 tooth from a 14 tooth and rear sprocket to a 38 tooth from a 39 tooth. Gained top speed but lost some power. Added Stage one Hot cam and Uni airbox vents and gained power back. Added nerf bars, case saver(front sprocket), handlebars, new o-ring chain, handlebar hand savers, and 1/4 thick rear swingarm skid plate. Dynojet jet kit (stage 1 and 2) is on it's way along with new grips and twist throttle. As I bought it(with the spark arrestor removed from the muffler) I could take a 2006 yamaha YFZ 450 (with everything GYTR except cams and hotbox) off the line in a drag and due to dust it couldn't catch up (five consecutive races swapping bikes the 3rd and 5th race). The 450 is too light to get traction off the line and once it gets traction it's either too far behind or has to downshift to get back up in the RPM's. Since I've added my modifications we haven't dragged but have done a lot of tight trail riding together. We're pretty equal with the exception of slow tight corners and areas that require a lot of torque and lugging. No contest. The YFZ stalls out or has to spin the tires to get through it and most often gets stuck. I've made it a point not to follow him through the trails since he holds me up having to constantly restart his motor or my having to find away around him to pull him out. So far I have about $5200 total invested into my 400ex. $4200 being the initial cost.

i8amm