400ex performance mod questions
Oct 30, 2001 | 04:02 AM
#1
Thread Starter
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Weekend Warrior
Joined: Oct 2001
Posts: 3
Likes: 0
i just bought a 2002 400ex about a month and a half ago. i really like it so far, but it could use a tad more umph.i want to make a few basic mods. what i want to know is what would be good for trail riding in the woods? i have heard a k&n filer kit, and a white brothers exaust. if so should i mess with the air box lid at all, and should i go with the full exuast? also is there any other mods to do. how reliable is it going to be with a few mods? one final question- this may be stupid but,it seems as if there is a bit of a power loss in colder weather like below 45 degrees (yes the engine is warmed up)is this normal, i always kinda thought so, maybe im just getting too paranoid about my new toy. thanks for any help
Oct 30, 2001 | 10:23 AM
#2
Trailblazer
Joined: Sep 2001
Posts: 93
Likes: 0
Congradulations on your new toy!!!! I understand how you feel about wanting a little more power on your 400ex but still keep it as reliable as it is when it's stock. I can anwser some of your questions for you.
I would definately start by getting a new exhaust system. It's hard to say which one is the best, it just depends on which one you like the best. You don't really need to purchase the whole system either. Yeah, a complete system will probably produce more power, but it costs a lot more just for a couple more horsepower that it puts out. I just bought a slip-on FMF Powercore IV. I like it a lot, and I am very pleased with the increase in torgue and HP. It also sounds good as well. It sounds like a real 4-stroke should sound like but it isn't abnoxious. I would also definately install a K and N powerkit. That includes a K and N filter and a Dynojet jet kit. That is all the engine mods that I did to mine because I as well want to still have a reliable machine. Of course there are many other engine mods that you can do, but in my opinion, you are taking a chance when you start messing with other stuff.
The pipe and air intake w/ the jet kit are the only engine mods that I did to mine and it has an awesome increase in torgue and HP compared to a stock 400ex. I did a lot of body work to mine as well. Everything is listed below.
If you mostly ride in the woods on trails that's really all you need to for engine mods. You are still going to have a reliable machine. The pipe and air filter are easy to install. However, you might want to have someone who knows how to rejet carborators install the jet kit.
As for the power loss in cold weather. I don't really know how to anwser that. However all Hondas are cold blooded as you probably already found out. Especially a new 400ex doesn't like to run in cold weather. I guess that the new motor and cold weather don't mix. I wouldn't worry about it though. I hope that I helped you out. Thanks.
Fourtracker14
I would definately start by getting a new exhaust system. It's hard to say which one is the best, it just depends on which one you like the best. You don't really need to purchase the whole system either. Yeah, a complete system will probably produce more power, but it costs a lot more just for a couple more horsepower that it puts out. I just bought a slip-on FMF Powercore IV. I like it a lot, and I am very pleased with the increase in torgue and HP. It also sounds good as well. It sounds like a real 4-stroke should sound like but it isn't abnoxious. I would also definately install a K and N powerkit. That includes a K and N filter and a Dynojet jet kit. That is all the engine mods that I did to mine because I as well want to still have a reliable machine. Of course there are many other engine mods that you can do, but in my opinion, you are taking a chance when you start messing with other stuff.
The pipe and air intake w/ the jet kit are the only engine mods that I did to mine and it has an awesome increase in torgue and HP compared to a stock 400ex. I did a lot of body work to mine as well. Everything is listed below.
If you mostly ride in the woods on trails that's really all you need to for engine mods. You are still going to have a reliable machine. The pipe and air filter are easy to install. However, you might want to have someone who knows how to rejet carborators install the jet kit.
As for the power loss in cold weather. I don't really know how to anwser that. However all Hondas are cold blooded as you probably already found out. Especially a new 400ex doesn't like to run in cold weather. I guess that the new motor and cold weather don't mix. I wouldn't worry about it though. I hope that I helped you out. Thanks.
Fourtracker14
Oct 30, 2001 | 03:09 PM
#4
Trailblazer
Joined: Sep 2001
Posts: 93
Likes: 0
No, you don't really have to get new sprokets. You can if you want to but I don't think you really need them. As for getting both front and rear, I would just get the front one unless you need both. I have never had to replace any sprokets on any of my machines that I have owned.
Fourtracker14
Fourtracker14
Oct 30, 2001 | 04:57 PM
#5
Pro Rider
Joined: Jun 2001
Posts: 1,089
Likes: 0
It's odd you have power loss in cold weather. If anything you should get quite a boost of power once your engine is warmed up. Cold air is denser the warm air so as the temp downs you get more oxygen molecules into your mixture and eventual into your cylinder allowing you to burn gas more efficiantly.
I would think that if you are experiencing power loss, it's because your mixture is perfect or just a little lean during the summer. The cold weather might just be pushing you over the edge. I would try going one step higher on you main jet for the winter and seeing what happends. Properly tuned engine you should get a nice kick in the winter. To put it into perspetive I read a test in performance car magazine about 2 years ago where they dynoed a mustang 5.0 and a Integra GSR. The conclusion was that for every 10 degrees the temp dropped both car experienced a 1-2 HP gain across the board. Now don't expect to get these same results at home on your car, at least not for long. It was also discovered that once the engine compartment got warmed up most of the extra HP was gone. Enter the "Cold Air Intake System". This is an aftermarket air filtration/intake system availiable for some cars and trucks that incorporates a high flow filter (usually a K&N) along with a new intake duct that allows the vehicle the breath cooler air outside the engine compartment. I have experimented with this extensively and can testify that they work very well. And when the temp drops really low your get one hell of a boost. Sorry i am rabbling on, I love turbos, NOS and all intake related stuff.
I would think that if you are experiencing power loss, it's because your mixture is perfect or just a little lean during the summer. The cold weather might just be pushing you over the edge. I would try going one step higher on you main jet for the winter and seeing what happends. Properly tuned engine you should get a nice kick in the winter. To put it into perspetive I read a test in performance car magazine about 2 years ago where they dynoed a mustang 5.0 and a Integra GSR. The conclusion was that for every 10 degrees the temp dropped both car experienced a 1-2 HP gain across the board. Now don't expect to get these same results at home on your car, at least not for long. It was also discovered that once the engine compartment got warmed up most of the extra HP was gone. Enter the "Cold Air Intake System". This is an aftermarket air filtration/intake system availiable for some cars and trucks that incorporates a high flow filter (usually a K&N) along with a new intake duct that allows the vehicle the breath cooler air outside the engine compartment. I have experimented with this extensively and can testify that they work very well. And when the temp drops really low your get one hell of a boost. Sorry i am rabbling on, I love turbos, NOS and all intake related stuff.
Oct 31, 2001 | 02:51 PM
#7
Pro Rider
Joined: May 2000
Posts: 623
Likes: 0
I've got a Dyno-Jet Stage 1 jet kit for a 400ex never used still in the box. I'd let it go for $40 including shipping. The Stage 1 is for piped EX's only.
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Oct 31, 2001 | 03:16 PM
#9
Trailblazer
Joined: Sep 2001
Posts: 93
Likes: 0
Yellow7,
I ordered the headlight covers from Nac's racing. My shockwares I bought in a store in Michigan called David Allen Racing. I also purchased my K and N powerkit in a store. All of those things can be ordered out of a catalog as well. You have to call Nac's about the headlight covers, but the shockwares and K and N kit can be bought or ordered from anywhere.
Fourtracker14
I ordered the headlight covers from Nac's racing. My shockwares I bought in a store in Michigan called David Allen Racing. I also purchased my K and N powerkit in a store. All of those things can be ordered out of a catalog as well. You have to call Nac's about the headlight covers, but the shockwares and K and N kit can be bought or ordered from anywhere.
Fourtracker14