I'm interested in putting a larger piston in my 2000 Honda 400ex. I have a few questions.

1. What performance difference is there between the 420, 430, 440 piston for the Honda.

2. I am 6'2" and weigh 250 lbs. What piston would you reccomend based on my weight. Most of my riding is motorcross track or sand dunes.

3. What do I need to do to the engine in preparation for the new piston. I imagine I need to bore it out- anything else? (I'm new to this)

4. How much (average) is it for a machine shop to bore the engine- I would prefer to do the rest of the work myself.

5. How detailed are the instructions that come with the piston?

6. I've heard about people upgrading their: CAM, Carborator (bigger), rejetting, etc... are any of these necessary? - Which would you reccomend?

7. With a 440 upgrade- do I need to do a "race fuel" mixture to maximize performance?

Thanks for all the feedback!

B

 

Hey Rot Gut;

1. the performance difference is noticable between a 406 and a 440, but going straight to a 440 means a sleeve and no more bores left. Here are your options on piston diameter - standard bore, .+040" 406cc, +.080 416cc, +.120" 426cc. You can go to a 440cc (+.160&quot but must sleeve to do this and to do it correctly, the case has to be modified to accept the larger diameter sleeve (you can by 440 sleeves that don't require cases machined, but I have heard that they have cracked because they are a little thinner. I would suggest going to +.040" with a bigger piston, that way you have 2 more bores left. The standard bore may be o.k., but will need to be inspected and honed to a good cross-hatch pattern.

2. Your options on pistons are (stock is 9.5 to 1 compression or right around there). 10:1 compression - wiseco pistons/ 10.8:1 compression JE pistons/ 11:1 compression wiseco / 12:1 compression JE. 10:1 you can run pump, but will not feel a large difference over stock, 11:1 is about the breakover between running pump gas and race gas (mix 50/50 to achieve 100 octane) you will feel a noticable difference over stock and 12:1 race gas only, you feel a lot of power, but the higher compression comes with more heat and less reliability. Having said all of that I would suggest 11:1, I am running that right now and am happy with it. Depends on how fast and how much reliability you want.
With your type of riding (MX and dunes, high rpm), you will want to think about pumping as much air through it as you can and maybe a different cam setup than I run (I race woods).

3. In preparing the engine, would clean it spotless and a clean environment before you start, otherwise, you should pick up a 400ex service manual if you haven't already - it will pay for itself 10 times over.

4. Machine shops generally charge from $30 to $45 to bore and hone it. Make sure they use a boring machine and if possible a boring plate.

5.Putting the piston in is breeze, the piston kit will give you info on the rings and piston placement, the rest of the instructions come with the service manual.

6. With just a piston change to 11:1 you should be o.k. on your jetting, since you are already at 165 main, which sounds a little rich (if the top of your piston is severally carboned up this will indicate too rich). I am at 165 right now and I have a cam and a few other mods and I am still just a tad rich. Cams other than the XR cam or TC cam are generally made of a harder material and require your rockers to be hard faced, which is an added expenses. However, with the riding you do you may want to thank of something different the XR, call TC racing or ask around some more.

7. Octane requirements are based on compression rather than piston diameter, so roughly 10:1 pump 11:1 50/50 or straight race, 12:1 straight race.

I will have wiseco 11:1 in +040, +080 and +120 in stock this monday and can get you a real good deal on the piston kit and gasket kit. If you are interested email me and I can tell you the particulars and save you some money.
If you decide you want a JE, you'll have to source them elsewhere, email me and I can give you their number to find a dealer.
Eadams747@cs.com

Good luck and glad to hear you are still showing the young punks around an MX track.

Later;
Nick
GNCC 426EX

 

Nick-

AWESOME information!!!!!! I do appreciate it.

I'm really looking for MORE power- so I think I'll jump to the 426- and allow myself one more bore. I imagine when I go to the 440- and it wears out... Honda will have picked up their dragging feet and come out with a serious racing quad.

My local quad shop said they would do a 440 kit for me for $1300. it blows my mind that I can buy a piston for about $250 and do all of it myself. I have already purchased the tech. manual you spoke of earlier. It's saved me ALOT of cash already.

You mentioned about carbon being on the top of my piston- telling me I'm rich- do you mean Spark Plug?

Again- your post was extremely helpful.

Brian

 

yea if i were you i would do that before ive had 3 setups a 416,440,and a 465 i just bored out the first time it was cool. I decided to go with the 440 from ims one day bam i snapped my rod in half causein it to come out the case luckly were good friends with a local shop and i get big discounts so i bought new cases and all new bearings had them bored out for the all new sleeve for the 465---this it what im runnin now i have 13:1 92mm piston and sleeve from sparks with a ducati carb i had my flywheel lightened im also runnin alcohol with a lrd big bore pipe its pretty quick i think...oh yea i also upgraded to a hotrod no more snappen ,the whole crank and everything has been balanced, and extreme cam crap and my heads been put on a flow meter.....

overall youll be happy IM LIKEING MY QUAD FOR ONLY BEING 16 [img]i/expressions/face-icon-small-smile.gif[/img]

 

damn dude-

Isn't that a bit expensive running alcohol - and hard to get? It seems like overkill- but then again- "overkill" is some people's hobby.

how much have you spent on your upgrades?

 

it wasnt that expensive.. me and my dad decided to do it...its just my once and a while mess around with quad.... alcohol isnt expensive one bit and add hp

 

Hey Rot gut;
The carbon build up on the piston will show rich or leaking valve seals. The discoloration on the plug also shows rich condition, just take a while to read on four strokes especially with a race gas that burns clean.

A 426 will do you well. 250 for a piston sounds awful high. I can get you an 11:1 piston kit and gasket kit for $130 to your door. If not that is cool, I try and keep 4 to 8 pistons in stock since there are numerous 400's around here and they always ask me for parts since I carry a lot of spares and do motor work.

Good luck with the quad, you will be happy with the 426.

Nick

 

you can buy over bores for the 440 !!!!

 

what does an overbore do? why would you need it?

 

a overbore is when you wear out your current clyinder you can have it bored to the next size .when the 440 overbore first came out that was the biggest you could go .....if you damanged it you needed to replace the sleve.. they now make pistons in larger sizes to acomidate more boring