i have a 2005 400ex, which i love. the handling, and suspension, and power is awesome. but you all know how it is, you always want MORE. does anyone have a big bore 400 ex, either a 426, or 440? if so would you mind telling me if it was a good investment. how does it compare to the stocker. i have a few mods already, just wanting to make my ex stand out a little more. any feedback on my question would be most appreciated. also are the rev boxes all they are cracked up to be?

 

Hey Leroy cant believe no one replied to this yet.

Anyhoo here is a little basic info and I know there is plenty more on here already if you do a little searching (try 416, 440, big bore etc etc).

Basically save yourself some extra thinking and just compare the 416 and 440 (unless of course you want a stroker and from 460-500cc, but there lots more $$$ too).

I dont bother with the 426 size because it requires the sleeve be machined to a point where many will argue its too thin, and the size difference from the 416 is so little that it seems to only make sense to go with the 440 and resleeve if you want to go larger etc.

The main differences besides the obvious bore and cc's between the 416 and 440 is the need to purchase the new sleeve and have it installed when doing the 440. Its an additional expense that is worth it if the $$$ are in your budget. Another is that though the 416 will benefit from a silencer, aftermarket cam valves and springs, and porting etc the 440 really needs them to work right. Sure it will run without them, but trust me that it will not be impressive without those few mods and can even be disapointing (mine was originally set up with low compression and only a silencer with all other engine parts being stk, and it was a dog after mid rpm).

There are some tricks to doing both too, but before I wear my fingers out I would want to know what your thinking (specifically) and also try to find some links to more basic info if you cant find it on your own.

After your ready to start looking into it more seriously (have cash in hand, and the info ready to make the decision etc) I would be happy to help with those little things that can make all the difference etc.

Good luck anyway you decide and enjoy what I still think is one of the better machines made when set up right.

 

since price is always an, issue, i figure i will use the 416 kit. no clue who makes it. i didnt see on ebay. didnt look too hard. also i will probably get a hot cam, or some kind of performance cam. do you really need new valve springs? or do they need to be a special kind. im not really experienced on motor work, and i would rather buy the parts my self instead of relying on a dealer to get his mits on my money accounts. i already have the basic pipe, and filter. i just want more power to compensate for the weight my wheeler is carrying around. 220lbs + gear. anyways. comments.

 

A lot is going to depend on how your mechanical skills are, and if you have patience to figure out what you dont know before just winging it etc.

This isnt brain surgery or whatever, but there are some basic skills needed and a couple of "tricks" that will make your results better and life a lot easier.

I get greif a lot over the " kit" issue because I am not a really big fan of them, and basically a kit is little more than the parts your needing, but picked by someone else based on profit potential, and I would rather pick my own based on quality, ease of installation, company, etc etc.

All that said you can make your own "416 kit" by purchasing a piston set (w/rings and pin etc) head gasket, and the other couple little things you will need.

Since your not going to be changing the sleeve your only left with taking the cylinder and new piston to your favorite machine shop and having them bore and hone the cylinder for you (could even have them gap the rings if you are not comfortable doing that). After this its all basically installation, and any other mods your looking at.

New springs are not required for the HC in either stage, but if you have the extra $$$ there not a bad idea. Going to a new one piece valve is a good idea too if you have the $$$ since you wont have to worry about the multi piece valves coming apart, but its not required. If your engine doesnt have many hours you would most likely be ok with just changing the cam, and wouldnt have the expense of the other parts, or reseating the valves etc., but if its got some time on it I would deffinately think about the new parts (actually I did, and got them all lol).

After you digest all of this you can start to look into those tricks I mentioned earlier. Remember that not all pistons are the same, and even ones with the same comp rating will produce various different results (actual compression v/s rated) You want to know what your new piston will produce, and the only way to do that is to take some measurements, and then make any changes that are needed to get your desired results.

Some people dont want to have to run race fuel, and thats understandable, but it requires you stay below a certain comp level too. If you dont mind to buy the more expensive fuel, and even mix it or run it straight etc then you can look at higher levels. One thing to keep in mind is that these higher comp ratios done come free and the additional energy created inside the cylinder may cause you to need to perform other mods to make it work without causing any failures (blown head gaskets are one, and what I am dealing with now myself).

I know there are some good threads here, and there is one on the site in my signature on the subject so take a look at different info and go from there. The one on offroadnj.com is geared towards the 440 but pretty much all of the info is good for any size bore.

Hope that helps

 

Actually you can go to a 426 without resleeving,anything higher and you have to resleeve.I went with the 416(12.5:1 JE piston)with a Web Track cam,1mm bigger intake valves,FTZ portwork,1200 (Advantage)more rev-box,Curtis Sparks exhaust.I have all kinds of torque,I can take off in 3rd gear launches with NO bogging in sand.I have outrun a 05 450R with the HRC kit by about 4-5 bikes,Predator with pipe,filter,jetting by about 6-8 bikes,04 Raptor with pipe and pro-flow ,jetting very handily.The good thing about the 416 is you still have 1 bore left.I haven't run any 440's but i've been told the 416's were faster,but I don't know this for a fact.Anyway I am VERY happy with the way this one runs!!!

 

I dont think anyone was claiming the 426 needed a re-sleeve, but rather that the size of the bore v/s the remaining thickness of the sleeve was what many believed was a problem due to the amount of heat these things can make.

Do you know what your actual or "real" compression ratio is (not the piston rating, but what the engine is actually producing)?

Reason I ask is that even though its not as large a problem with the smaller pistons as with the larger ones most of the time the pistons are not producing their rated compression. I have seen 11:1 pistons that only produced 8.4:1 compression, and that I am finding my original theory of high comp, high revs and advanced timing though a receipe for power are also a cause of problems with this engine.

I know your claims on the performance of the 416 are pretty accurate as I have seen some that really scream, and when done right (yours sounds like it is) can they can beat some respected models in a drag.

Have to remember that were only looking at 24cc difference between the 416 and 440, and only 43cc more than the stocker, but thats still approx 5% and 10% additional volume in the cylinder so there is more potential, but its the combo of all the other mods that really make the difference and as a package create the power.

Like I said earlier it can end up making too much power (or a combo of power and heat) and cause failures too. Honda may over design their products, but thats only true when based on their original power output, and when you start getting really good results from your mods you can get past the ability of the engine. I am currently in the middle of fixing one of these problems being blown head gaskets from the studs pulling out of the cylinder from the added force or energy in the cylinder.

My set up ran fine for around 2 years without a glitch, and was 100%, but I had set it up so that the timing was slightly retarted and didnt allow the engine to produce the full compression in the higer rpm's(mine is set at an actual 12.6:1). That caused the engine to pull hard in the low end to mid and then as the rpms increased it would fall off some, and though it wasnt the best set up for a drag machine (your 416 would prob be close or even ahead) it was easy to ride in the tight wooded stuff, and made better time than the same machines that would have given it trouble in a drag.

Well as someone who cant leave well enough alone I went and tried a new rev box with a 4 deg advance, and damn did it work well. It was immediately obvious that the change in the curve was making up for the retarted situation I had set up, and it pulled like crazy right up to the rev limiter. It truely made a big difference with my setup, but it also allowed the engine to produce more power, compression and heat in the higher rpms (now higher than ever lol) and I had a failure on the first day I used/tested it.

Where I am going with all of this is that first your set up is most likely not producing a true 12.5:1 compression, and thats potentially a good thing based on failures, and also that from what I am finding from my own time into this engine and talking with professional builders is that the additional heat and energy created within the cylinder when you do get all of the mods right and run high comp and high rpm etc can lead to trouble due to the additional heat (allowing the studs to be pulled from the added power etc) and also potential bottom end failures (rod etc) if you really push the envelope.

I had not thought of this myself but it seems to make sense that most MX riders will not see as many problems as XC riders due to the length of time the engine is running and producing heat. Even though both run hard and even a MX can produce conditions that will make the cooling fins cake up with dirt etc just the fact of the amount of time the engine runs, and that you cant allow the engine to cool between moto's in an XC race or even many hard trail rides seems to be what makes the difference. I dont race MX so I cant speak from experience or compare, but it does make sense.

I dont want to cause anyone to not be modding their engine because the majority of those out there will never see any of the problems since there not running the true or actual compression were talking about, and even a 12.5:1 piston may only be making 11:1 depending on the actual set up which will not create the energy, power or heat that it would at its rating.

Many if not most dont ever see any real problems, and even if you really take the engine to its limits there are plenty of fixes available from the time so many racers had put into this engine for the many years it was the best thing out there, but at least you can know in advance what your up against and be able to preparre for it.

Sorry for the length (I did edit it too before posting lol) but this stuff takes lots of explaining to make it understandable, and hopefully it helps someone out there, and maybe even sparks a little debate or exchange of info.