Hello everyone.. have been searching around online for information on the 400ex and came up on this forum. Thought this could be a great place to learn things. So as of 2 days ago I got a 2001 400ex my guy bought me. And it is completly stock and he wants to fix that.. I dropped 2 sprokets (if thats how its spelled) in the front. Now I heard that was bad he should of only dropped one. and just got a KN&N and a jet system for now. Since I am new to ridding I have always been on the back, very rarley ridding myself but I met this guy he owns a banchee and I had originally wanted a 400 because that is what I learned on but a few weeks ago I rode an artic cat and really liked that but anyway He bought me this 400 and Im going to learn to ride now.. but do you think the 2 in front is bad and he should change it to 1? and do the kNN and the jet thing?

 

the stock front sprocket on that bike has 15 teeth. dropping teeth on the front sprocket will drastically decrease the top speed. however, it will be great for trail riding or putting around where you need all the low end power possible. i guess it depends on your riding style. the smaller front sprocket will be more user friendly when learning.


i wouldn't really waste your money on a K&N and a jet kit. you won't get much of a gain. i do not know what your looking to spend but a cam and higher compression piston is the best gain for the money, even if you have a stock pipe. a good full aftermarket exhaust system will help out, especially if you build the motor a bit. i prefer the uni filters because they filter more air. the K&N, no doubt, will flow more but will also flow more dirt through. this is a heavily debated topic and everyone has their own opinion. when it comes time to jetting, i would just buy the individual keihin jets you need and not spend money on the whole jet kit. good luck

 

I would help you but would need you to post a picture of lilqtbarebutt. :-)

Ok, a little help. Only drop 2 in the front if you put 22" tires on the back. Highly recommend this if you ride in rocky or muddy areas. It would really be better to drop 1 in the front and go up 2 on the rear sprocket.

You will see some performance gains from opening up the airbox and rejetting. The main reason for doing this is it makes it much easier to start on cold days.

If it doesn't have nerf bars, get them ASAP. Same with a good pair of riding boots with ATV tread on the soles. One slip without boots and/or nets and you can kiss your ankle goodbye.

Let me know if you need help posting pictures.

/Jon

 

I will never understand why most riders think they have to fix a great stock bike as soon as they bring it home. Before changing anything you need to make sure that the bike is set up and maintained correctly. Forget about sprockets and different air filters for now. Give bike a complete service including valves, oil & filter, stock air filter check clean and lube,, swing arm pivot bolt before it's too late, all rear linkage, front A-arms, chain and sprockets clean lube and adjust. The stock 400EX will meet all your needs for quite a while and be much more fun to ride while you are learning. My 13 year old grand daughter rides my stock 400EX everywhere with stock gearing and uses mainly 2nd and 3rd gears in the dunes. Works fine for us.
I would ride stock until you want a pipe and then do the pipe, filter change, and re-jet all at the same time.

 

I went down one tooth in front, and didn't keep it that way for very long. When I would puch the throtle, the front end would reach for the sky! Powering out of turns, gets pretty exciting when the front end leaves the ground. It was ok for play riding around on a track, but riding cross country........not at all practical.

I would go back to stock. Ride it a while, then change one size, and see how you like it.

When you are ready for more power, vent the airbox lid (EHS Racing lid is great!), put on a muffler, and air filter (I prefer UNI to K&N).

 

I too am new to the 400EX, but am looking to get one this summer. With a completely stock bike, can hammer the throttle on a flat, dirt surface without flipping over backwards? If not, how much forward lean does it require? How about if you revved it quite a bit and then popped the clutch? If you lean forward, can you climb steep hills without the fear of flipping it? Basically, is the front end ridiculously light on a completely stock 400EX? Thanks!

 

The 400 will wheelie when you want it to, but it isn't so wheelie happy that you have to fear that it will wheelie unexpectedly. Hillclimbing is superb. Just lean forward a little if it gets light.

 

Excelent advice!!!!

I think we all get a little anxious and excited with the purchase of a new machine (used is still new to the new owner and just the same) and for those of us who have already spent unmeasureable amount of time and $$$ on our machines its easy to just start suggesting this and that because we have found it to be worth the investment etc.

I agree with leaving it mostly stock for the immediate future except for the safety type items (nerfs, tires, helmets and gear etc) and maybe some controls like new bars or a clutch lever etc.

There will be lots of time for modding it up later, and a new rider will be able to appreciate the changes more after getting some additional seat time on the machine.

Once the rider is more comfortable with the machine and has most of the safety and little items covered etc there are literally hundreds of performance mods avail for this model, and even more people who will be willing to offer advice.

I would be happy (as would be most others here too) to help you out with a plan for mods that match your budget and your performance gain expectations after your closer to being ready to actually make the changes.

You have a very good model there as its very predictable, forgivable, and easy to ride in stock form, but also can be made into a real performer if you should wish to go that route in the future.

Either way you decide have fun and go ride!!