newbie

[Helix]

I bought my 400ex new in 03. I'm familiar with riding it but not with moding it. Right now its 100% stock. I've always thought about adding performance parts to it but never have because stock is pretty much fast enough for me on trails. But now a buddy of mine just went and bought a new YFZ 450. So...now I thinking about some goodies but have concerns...

I just want to keep my quad as bulletproof and reliable as it is right now without having to worry about something going wrong all the time. I've been told just go with pipe, jet kit, and intake and thats it. Heard once you start boring, caming, stroking, etc. it turns into a whole different ball game! This true?

I don't know which combinations are the best for my quad. If I could stay with a yfz 450 without getting into the motor I would be happy.

:)

[Pipeless416]

Originally posted by Helix
I don't know which combinations are the best for my quad. If I could stay with a yfz 450 without getting into the motor I would be happy.

:)

i'm afraid that wont happen unless you just plain outride him. if he leaves his completely stock a well built 416 will keep up and still keep your reliability.

[Helix]

So the bigger you go on the bore, the more horsepower and less reliablity you go also?

[honda8&3]

I would say a 416 kit and a stage 3 hot cam would get u a lot faster than stock. Maybe an HMF Full system too. That is pretty darn fast and reliable set up there man.;)

hmm you want to beat a yfz450. Curtis Sparks x-6, rev box, stage 1 hotcam, k&n with out an airbox lid, of course jets. I would say you would beat him if he is running stock on these items. If you wanna cut some cost get an HMF full sytem but the sparks is by far the best. HMF second

[honda8&3]

Originally posted by FoxHondaRider
hmm you want to beat a yfz450. Curtis Sparks x-6, rev box, stage 1 hotcam, k&n with out an airbox lid, of course jets. I would say you would beat him if he is running stock on these items. If you wanna cut some cost get an HMF full sytem but the sparks is by far the best. HMF second

x2 sorry sparks is definetly the best for performance but for the money can't beat the hmf, with an fmf powerbomb header. That thing will fly with a lot of the mods listed. :cool: :devil:

HMF is 2nd best exhaust and yeah for the money you cant beat it! Soon 50% of quads will have HMF is they already dont haha

[CarGuy7a]

the only reason things can become unreliable with doing mods internally inside the engine is if they are not done correctly. if everything is done with care and high quality work it will be reliable.

yeah you should start with an aftermarket airfilter, exhaust and jetting.

[Helix]

I'm thinking HMF canister...but what about header? HMF as well or fmf powerbomb? Any particular websites your'd recommend for some ex aftermarket parts. There is several out there. But I'm sure there's some with better prices and shipping then others.

Appreciate the info!!:muscle:

[XXXRACER165]

I can beat a stock 450 easy with my mods. I have a 440 kit with a stage 2 Hot Cam, ported head, WB power kit (includes a Power filter, jets, and a E-series pro meg exhaust) and a Dirt Digger Clutch. Yet it's stone reliable.

[honda8&3]

Originally posted by XXXRACER165
I can beat a stock 450 easy with my mods. I have a 440 kit with a stage 2 Hot Cam, ported head, WB power kit (includes a Power filter, jets, and a E-series pro meg exhaust) and a Dirt Digger Clutch. Yet it's stone reliable.

Ya this guy has prolly 1 of 3 most powerful 440's on here. It is bad @$$.:cool: an FMF Powerbomb with an HMF Sport series is the way to go for the money. But the Sparks is awesome too.:cool:

[JDMThoughts]

Well if you follow the mod setup I have on my bike. You will definitely be a stock 450, as well as Raptor and Banshee. My bone stock Banshee gets worked hard by my 400. I have already beat a local guy with a GTYR equipped Raptor, and of all the 450s I have rode, YFZ included my 400 has way more power. I spent a total of 700 on all my power parts. The only thing left is to rip the motor apart. The exhaust is loud, but build up the top end of the bike nicely. The air induction setup is also very cool. The timing key is alledgedly worth 2-3hp but I am not sure, it definitely has instant throttle response right now. The bottom is nice and strong and the mid range is killer, but the top end still isn't amazing, like on a Banshee. You can get even more power using a Sparks rev box, because that advances your ignition timing another 2 or 3 degrees. I am extremely satisfied with my Sparks setup. HMF is also top notch if you wanna save a few bucks and wanna color match your rig. If you order from Sparks now, they have a kit with your exhaust choice, air filters (I received 2 for some reason) and their jetting kit for 620. I also picked up an EHS open air lid and love the quality in that piece as well. Hopefully this helps you out.

will the timing key ruin the longevity of your machine? a rev box can make you blow up, i've seen it done

[JDMThoughts]

I haven't heard anyone talk about a rev box blowing their bike up. An idiot who tries to hang in the upper 3000rpms in every gear will destroy a bike. Adding the rev box, gives a slight increase timing advance, but more importantly lets the motor rev higher. I can be honest, when I got my bike back, I hit the limiter at least 5 times that day because it pulled to the redline so fast. The timing key is a cheap 15 dollar part that improves the throttle response and adds a couple hp. The motor won't blow up because the risk of detonation is so low, the compression on the 400EX is obnoxiously low. Adding the key and rev box will definitely liven up your bike. My only suggestion is that if later down the line you go to a higher comp piston, depending on your ratio your going to need to either take out the timing key or run race gas. If you run 87 octane owl piss in your bike than maybe I would upgrade, I choose to run 94 in both of my bikes, the extra octane is worth it, whats an extra 65 cents a ride vs. a blown motor.

[250x_kyle]

yes the bigger the bore the less reliable it is. although if u send your motor out to ritter cycle or duncan or a place like that im sure that you will not have a problem with reliability.

[Helix]

Thanks for all the information guys. Your a big help! Like I said I'm pretty new to modifing my quad so...I just want to go about it the best way possible, thats why I came here. I just have some decision making to do now. I definitly want holeshots but what kind of holeshots do you recommend? Can a piped and jetted 400ex benefit from a bigger carb like a 39mm of some sort? Or would it not be necessary on stock bore? One more thing. My brakes have been spongy since the day I brought it home. I don't think theres any air in the line. Would new pads fix this or is it more of a caliper problem? Which kind are preferable?

JDMThoughts do you still have the stock carb? I guess you do since you don't have it listed.

[j450rking]

i use ebc sintered metal pads and they work great for me others might say stock honda pads are better but i don't think so they might last a bit longer but they don't work as well as ebc's.

and stainless steel brake lines will help with that spungy feeling.

other then that just use 3m silicone past on the slider bolts and stuff on your calipers and you will be good to go.

and i have a 416 kit stage 2 hotcam and all the other mods in my sig and my ex is vary fast i have beat a yfz 450 with a good rider on it by about 10 feet

[JDMThoughts]

Originally posted by Helix
I definitly want holeshots but what kind of holeshots do you recommend? Can a piped and jetted 400ex benefit from a bigger carb like a 39mm of some sort? Or would it not be necessary on stock bore?

JDMThoughts do you still have the stock carb? I guess you do since you don't have it listed.

I am still running a stock carb, because I am don't have any big bore setup... at least not yet. The carb isn't the limitation on the bike in stock form. You would get a bigger gain in power by swapping to a higher compression piston since the compression is terribly low. Hence the reason I am advancing the hell out of my timing. If you can't get good holeshots, that's more of a rider issue, it's not really the bike. That is something you will need to practice. Sure you can upgrade to a bigger carb and get some power out of it, but I will tell you this, your camshaft is only gonna let so much air into the motor, and the head porting will only do the same. Having that bigger carb would be awesome if the rest of your motor could support that airflow.