I have been considering on the purchase of some sort of engine kit to get more ponies and speed out of my 400EX. For the longest time, I was sold on the 440 kit with cam, high comp. piston.... but now I am considering the 416 route. I read in the Sept. 2000 4Wheel ATV Action mag, about a 416EX racer. Engine wise, all it really constists of is a JE 87mm piston, ported/polished head,WB Full Race cam, stock rocker arms w/ a hard face material(for longer wear), some hole drilled in air box, White Bros Pro Meg System, and a WB rev limiter. With all this it produces 40 HP. The advantages of the 416 route compared to the 440 is that the 416s piston is lighter and allows it to rev higher and quicker(meaning faster on top), and vibrations are to a minimum. The bore and stroke are perfectly balanced too. And with a rev. limit of 9600, the 416 can run at full throttle all day long. They also said that it was rock solid, never missed a lick. So which is the best route. It would seem to me that with the smaller displacement that it would also get better gas mileage too, right? I want these mods for the MX track and straight line speed. My goal is to beat my friends 2000 CR250R with FMF Fatty. But thats probably never going to be possible unless I turbo charge it huh? Please let me know your thoughts. Thanks

 

Oh, now come on guys. I know you have an oppinion on this Topic. You guys are always talking about engine mods, and stuff. Any help would be greatly appreciated. Thanks a million.

 

I went with the 416cc bore, a 10.5:1 compression je piston - this allows me to just use high octane pump gas, no hassle. Ask far as I've read in the forums, the 440cc is nice if your looking for tons of torque, but understand the 416cc may be a shade quicker because you've got a lot less mass to throw around in the motor. I also put on an IDS 2 supertrapp pipe. I planned on putting a hotter cam in, but from what I heard I decided not to cause it tends to make more power on top, but somewhat reduces power on the bottom.

Results: More power everywhere, especially on the bottom and midrange - very quick compared to stock. I throw roosts around like a two stroke now. A friend commented on how the midrange power feels more like a 2 stroke than a 4 stroke - but without losing the low end grunt.

Do yourself and your pocketbook a favor and do your own work without buying a kit. Pick up any good 400ex repair manual (I used a haynes); it goes step-by-step on removing components (with pictures) and torque values when you reassemble. Just bring your new piston and cylinder into a good machine shop or dealer and have them bore it out. If you get hardened rockers and stronger valves/springs they will install those in your head too. My bore cost $65. Order your je piston directly from je. Get a gasket set from your dealer or any good aftermarket company. Get your cam, hardened rockers, etc. from powroll (they are incredibly nice and helpful).

You will learn a lot from the experience; if you can use a screwdriver, wrench, needle nose, vise grip, loctite and a torque wrench, and can read step-by-step instructions, you're set.

You'll be very pleased with the power gains; I'm hard to please and my 416ex even put a smile on my face.

ogre

 

When I said buy a kit, I didnt mean to purchase it and let a dealer do the work. I am very much mechanicaly inclinded and am capable of doing all the motor work myself. I just want to know, which displacement 416 or 440 is the best for top end speed and acceleration. Thanks for your help tho.

 

based on what has been said plus i betthe 416 is cheaper, i agree the 416 would be better. And also, I'm sure in the long run a 416 will have much more engine reliability than the 440, not that the 440 doesnt...so forget that argument. But i think the 416 would be cheaper?

 

Yes, the 416 is cheaper, no new sleave to buy/install.

VilentJ, I certainly mean no offense and did not mean to insinuate that you are mechanically disabled, I just didn't know your experience level at the time of the posting. Futher, there are many out there that maybe on the fence about purchasing a "kit" for two to three times the cost of just "picking up" the parts. If they just take the time to look over previous posts regarding this issue, they will find all the answers they need, and save a boatload of cash.

At any rate, I had a blast building my 400; quiet, peaceful garage - working at my own pace, and best of all, the general smell of "motor work" permeating from my 400, filling my garage with the wonderful smell you get when you walk into a dealership. I think that may well be my favorite smell of all.

ogre

 

I have the 440 kit and love it, although I believe the 416 or 426 to be better for MX racing. I have heard that 440's are not allowed at some mx courses. I myself race cross country, so there are no limitations to displacement, and my 440 is well suited for such.

 

now i'm not the smartest at this boring and jetting topics you guys talk about but i do know a little about these. i've never bored anything and i just want to know that if I get a 416 is there any boring required and how much??? now i've heard about a 406 and someone told me that all i'd have to do is just remove the sleeve and isntall the piston. now doesn't that mean thered be some problems???? well please reply thanks

 

top end speed and torque=440 kit . ther is no replacement for dicplacement.you might have to gear the 440 for more top but it'll get there quicker.price wise a 416 0r 426 is alot cheaper and will still pull nice.your choice-i went with a 426(pricewise)and am very happy.it also depends on all other mods not just displacement.

 

If u really want the most potent 400ex engine u have to go with the TC416 national kit. it is abouslutely awesome. It is not the displacement that matters, but more the porting. The kit goes for about 1700 but it is the most competive kit u can get..

later