So I just purchased a 05 400 ex with a few cheap performance mods on it but need some help on what to do to maximize the power from it. A week or so later my dad bought a 05 Honda 450r bone stock and it's way faster. I'm gonna jet my carb to match my exhaust set up and drop to a 13 tooth front sprocket and eventually step up to a 42mm carb...Will I be able to get close to the 450r???
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If going as fast as a 450 class machine is your plan, sell the 400 now before you put any money into it. On tight woods trails rider ability can play into it quite a bit. In the open stuff the 450 just has to much power and the low tech 400 motor can't really be built to reliably compete. Plus you get much better suspension. Or itnis possible the 400 is better suited to your riding style and trails and may be the preferred machine for both of you. A 450 has some edge to it, they like to be ridden hard and need frequent maintenance.

Bottom line, if you want to do a little work to your quad to make it better/faster etc that's fine. If you need to make it 450 fast and 450 class drawbacks are ok with you, just start over with one of those.

Also, what has been done to it so far?

 

Just a powerbomb header and big gun es exhaust. I don't think the previous owner jetted the carb to match. Also has a k and n without the airbox lid. I think I'd do well on the 400 in the trails, and I ordered the 13 tooth front sprocket. Any advice would be much appreciated

 

K and N are junk for anything but sand. I would throw a foam filter and look for an aftermarket air box lid like outerwears. Check the valve clearance and call it a day. Big Gun tends to be loud and not make any more power than any other, but realistically you won't gain much with a newer exhaust. The carb upgrade isn't really needed unless you are going with a large overbore. Since it has been run with no lid, you may be looking at a top end rebuild sooner rather than later. Maybe throw a 416 kit on it at that time, should wake it up a bit.

 

I've heard that about K and N, this quad won't be seeing any sand so I'll take your advice and switch to foam with the modified lid. Seems like I should have done some more research before buying the 400, it will definitely serve its purpose for what I want it for I was just surprised by the difference in the 450. Especially since they are the same year.

 

Nothing wrong with the 400, but it just was designed with a different purpose in mind. It is a very well rounded machine that does a lot of things well, just not as fast as the race oriented 450 class.

 

You're 100% right. I was just unaware of how different they were. Should have rode a 450 first or just bought the 700 raptor I actually wanted lol.

 

Oddly enough, the 700 is somewhat a combo of the two but also it's own beast. They don't handle as sharply as either the 400 or 450. Make plenty of power, but it is a torquey lazy power suited well for trail riding and dune shooting. The suspension is nice and cushy though, and a great place to sit your backside for a long day on the trails.