Saw this on the main page of this site and wanted to comment on it because I thought it was a very well put together piece, though not 100% complete. For the sake of helping our members better understand the entire process and avoiding some potential problems I wanted to offer some additional info and hints that can save you some trouble or get you additional gains beyond basic kit.

Before we get into the technical stuff a big thumbs up to the author James Graham of the ATV Connection Staff for finding and taking the time to detail all the various steps involved in the process of upgrading the 400ex into a 440ex.

After reading this I have to wonder if the author had done any research on this mod on the atvconnection forums as I know this subject (440 kits) has been discussed on the boards here more than once. Just to be clear I am not attacking the author in any way (yes not even all the obvious mentions of Wiseco, or how some could consider it an advertizement etc) and am actually applauding him for doing the article, but with so many things missing that seriously effect the overall performance of the big bore set up on this engine I feel its only proper that some things be set straight so that others are not mislead etc.

One thing that everyone needs to remember from the article no matter how much experience you may have with this model is to deffinately have a repair manual for reference, and its also not a bad idea to spend a little time reading thru the engine sections prior to starting this project. The time and aggrevation it will save you (not to mention and additional parts) far outweighs the cost of the manual.

Some of the suggestions here are actually things that are required in the manual, and also will save you from running into trouble with other things later during the re assembly (tying up the cam chain, having the engine at TDC before tear down etc) and these are good ones, but its the missing ones that will have you thinking about tearing it down again later that I will discuss below.

For those not that familiar with the history of the various 440 kits made for the 400ex and the many little problems that have been part of those kits history this story sounds like a great way to make your 400ex a much better performer, and it is but the potential for additional gain and less "pain" are as large as those found from the mod performed in this story.

I wont get into nit picking on any of the missing assembly stuff etc, and am going to address the major points only. I am sure any of you who have done this yourself can discuss all those little things later.

COMPRESSION RATIOS:

Lets look at the beginning when these "kits" first became available. Though both the major known piston mfg's names in our industry had issues with discrepencies between their advertized compression and actual compression ratios (the piston ratings were much above those the engine actually produced) it is generally agreed that the Wiseco kits were seeing the largest difference from their ratings. This discrepency was caused from two different things, one was that the mfg's had set up their ratings based on the xr400 which had slightly different deck heights (the distance that the piston is either above or below the top of the cylinder at TDC) and another is a percieved attempt towards preventing rod and crank damage by having a lower than advertized compression.

Over time much of those discrepencies had been reduced but to my knowledge the first company to address this was Ross Racing Pistons, and though the others had followed suit what I found from my phone calls to all three companies was that Ross offered the most accurate and indepth info on what actuall compression ratios could be expected from your current information and engine etc.

So now that we know that the compression ratio you end with may not actually be what you were expecting from the pistons rating lets look at how to address this and get the ratio you desire. The real points to take note of here are the deck height, piston dome and gasket thickness (though there are others that effect it too) all of which will effect the actual compressin ratio.

Since compression is the major thing that causes your engine to produce power (torque) this is a very important part of your engine set up. Those of us who have had 440 kits (most are only 431cc anyhow) that were only making 8.5:1 to 9.0:1 comp but rated at 11.2:1 or more and had to correct the problem already know how much compression can be gained by a simple change to thinner cometic gaskets, or having your clyinder decked (removing so many thousands of material off the cylinder making it shorter etc). This can be looked at as the main important item when setting up your engine, and no matter what other decisions you make later on (cams, pipes etc) you will benefit from having the additional compression you were expecting.

I cant tell you what the author ended with as a actual compression ratio, and he may have gotten lucky and its close to what he expected, but you can be sure of this just by taking a few measurements and making any needed changes. Though the right way to measure the true or actual comp is a little tricky and a bit messy (it requires you to cc the cylinder by measuring the amount of oil or other fluid it takes to fill the cyl and using a formula to figure the amount of comp) there are several on line calculators avail to us that allow us to type in some numbers (most info found from measuring your engine and or a call to the piston mfg) and even make changes to the gasket thickness or for any decking to see what needs to be done to get to the desired comp ratio.


INTAKE AND EXHAUST:

A large mistake many have made when moving up to a 440 is to forget that the larger amount of cc's require different mods than the stock bore to perform properly. Many of those doing this mod already have an aftermarket exhaust or silencer that is freer flowing than stock (some too much free flowing and loud) and thats a good start but now its time to get into cams, valves, carbs, and even intake mods if we want to see the full benefit of the increased engine size.

I know that many have done just the same as the stories author (including the original owner of my honda) and basially bolted in the parts needed for the 440 and went riding, but if you want to get full advantage and not end up with a with a bottom end only engine that falls on its face after 5000 rpms (especially the ones with the kits making barely 9:1 comp) and prefer an engine that pulls like crazy from bottom to top your going to need to make this engine be able to breathe and basically compliment the larger bore and added compression.

First thing that absolutely has to be changed out is the cam. Everyone has their own idea on what cam or cam specs are best but the gains from the smaller grinds (xr cam, hotcam stage1 etc) are minimal and better suited to mostly stock engines with basic exhaust mods. For the added amount of flow needed to allow the larger bore to work properly you should be thinking more into the larger cam grinds ( hotcam stage2, web 450-451, WB track cam, etc) and should also consider complimenting them with a better set of valve springs so your sure the valves are not hanging up (a bad thing when running closer valve to piston clearences from increased comp and larger lift cams that can in extreme cases cause contact between the valves and piston). Some will also recomend larger valves, but many dont agree (even some well known engine builders) and personally I didnt find them worth the cost, but this is not as important an issue as the others and you can proceede either way you like, and the stock sized valves have worked well even up to 500cc.

Another point that should be made is that the larger cams mentioned are mostly all "mid to top" cams, and though you can set up your engine to still makes lots of bottom end torque there are other cams with slightly less duration and increased lift that would be better suited for those desiring a stronger bottom end grunt. I have seen people get great results from the web479 (I am actually installing one very soon) and another web grind I dont recall the number of, and both of these are supposed to smooth out the power delivery where the others have a noticable mid or higer "hit". So it would seem the track type cams could be better suited for mx or drag racing etc, and the "bottom end" ones better for trail or XC racing etc.

Either way you decide on cams and even valves there a needed mod for your 440 to work to its expectations and best.

Another item that is very benficial to a well built 440 is porting. Though this is something better left to the pro's there is no reason you shouldnt understand the basics. With the increase in engine size and all the benfits of cams and other mods you will be able to see good gains from even a basic porting and polising. I wont get too much into the tech end of this process but basically it is removing obstuctive and uneeded material from the intake and exhaust runners in the head, and also enlarging the runners to allow additional air and fuel into and out of the engine (increases flow, and or velocity) without obstuction.

Porting and polishing can be considered an art, and if your artist over does it you can actually see a decrease in performance, so be carefull in how you decide on getting this done.

The stock carb is a good unit, but if you want to get full advantage of your new mods (your in for some serious $$$ already [img]i/expressions/face-icon-small-smile.gif[/img] ) you will want to consider swaping it out for a larger one. This is another area where many have difference of opinion but the ones that seem to be more popular and work best are the FCR39 and edelbrock eichner series. I dont have any experience with the Edelbrock but it seem to work for those who can figure them out, and the FCR is embraced by everyone I know who has one. This is a mod that isnt a requirement (I have been running a modded stocker with great results, and cant wait to compare it to a FCR later this year) but one that will add to the overall performance and there only around $450 or so.

So if you want to be competitive with the newer models being sold today you do have options besides losing money on your 400ex and buying something new to start moding all over again, but you need to learn some of the tricks and be able to get it done right if you want to get the performance gains you need to stay with the newer technology.

Sorry for the length but finally I have put most of the main issues to be tackled in one thread!! Also I hope this helped those looking to move up to a 440.

 

I appriciate the time you took to write that all out!

 

Shavo no problem and hope it helps etc

Have to admit with all the questions I see and help people with that I thought this would get more replies, but maybe I answered much of the questions already.

Anyhow it was about time I got it all out in a thread at once so maybe I could help someone avoid all the extra time and work I had to put into this when I first got into this engine.

 

wow, very well put, this will be VERY help full for 400ex owners. Thanks for taking the time to explain this, this should be made a sticky

 

i believe the deck height on the xr and ex are the same. however, the gaskets DO differ. good article.

 

Hey thanks to you both for the thumbs up etc

As far as the gaskets are concerned I never have gotten into an actuall xr400 engine, and it could be the head or base gaskets that are thinner (or even both) but I do know that the original and even some later pistons were designed for the XR and only adopted to the 400ex so that is where some of the issues come from.

I cant tell you why the later pistons dont produce the advertized comp ratios (well the why is sort of obvious so I can tell you that, but why the mfg still allow it to happen is what I cant explain) but then if you use some simple steps to setting up any engine with some basic measurements etc you can be on top of the game and better able to get the results you want etc.

Now there is just one other long "how to" thread similar to this one that I want to do, and its going to be about general hop ups and how to compare certain aftermarket parts etc, and hopefully it wont take as long to get going as this one did [img]i/expressions/face-icon-small-smile.gif[/img]