improving mid range and top end??

[trailrider894]

my 400ex is just kinda lacking in the top end and mid range power. so like on trails and stuff when they are real technical it does fine. power out of the corners with wheelies and stuff almost to much power. but then i get out drag racing up my driveway with some people and i just can't keep up. and the one guy has 300ex!! i just don't get it. it just seems like the power stop at half throttle. it has always been this was and i'm just sick of it. does anyone have a suggestion that doesn't require boring out the engine?? i'm open to anything else just not boring it out. and please i do have a tight budget so keep it low!! i already have a pipe (white bros e-series) and aftermarket header (fmf powerbomb).

[katch26]

whats your jetting/gearing?

[400exrider707]

Air filter (UNI)
Ditch the air box lid
rejet
cam.

Should wake it up a good amount.

You can also just do a higher compression piston on std bore. I did a piston/cam combo on my 400ex when I had it and it felt like a whole new machine. I went 11:1 wiseco with cometic thin head gasket and a stage 1 hotcam. If you do dig into the motor for any reason, replace the stock cam chain with an 02 CRF 450 chain (same thing as a heavy duty one, at a fraction of the cost)

You're right too, when mine was stock my buddies 300ex would outrun it, and I never figured out why.

[KEVIN300A]

Thats EMBARASSING A 300EX!!!!! will need more info man... what does it do spit or sputter backfire... or just literally stop pulling??? did u change the jetting to your new pipe?? stock airfilter?? also whats your gearing??

[ti2ibal1]

A Uni air filter, HMF slip on and re-jetting the carb really woke mine up in the mid-range. I've always been happy with the low end of the power band, but was pleasantly suprised with what the upgrades did for me. I don't do much wide open riding, so I can't comment on the top end.

Assuming you are still running stock jetting, I would say get a Uni filter and a 155 main jet. Start from there and see if that helps.

Outrun by a 300ex? Something is off for sure...

[UNBROKEN]

depending on how u ride i didnt like my stage one cam that much i could feel the power sighn off to early i would def get a 11/1 piston thin head gasket and stage 2 cam along with a filter and new timming chain

[witech]

Adding bore or compresion to an engine boosts the bottom end power. For top end you need more airflow which is porting , valve and cam work to let the engine breath. Retarding the cam timing also raises top end power.

I don't know about other exhaust's, but the alien I have is really high-flow, and between that and the timing key, my 400 has tremendous top end and mid-range over stock.

You can also consider getting your flywheel lightened.

[katch26]

I think the root of the problem is getting overlooked, you need to figure out WHY its topping out so early otherwise these mods will just get you to the same problem faster. Flywheel will help it rev faster but is not a power adder, cams and stuff really arent either (per se) just shifting power from here to here. Now before anyone kicks that out just look at a dyno of a stg 2 vs a stage 1. The stage one will have more.....its just moving the curve and adding a little peak at the cost of some down low but if he's breaking up for something different he will never even hit the band high enough to notice the difference.

this is what I would check
1. gearing - not sure if you bought it new or used but if its used than the previous owner may have wanted more down low grunt and either dropped a tooth (or teeth ) in the front or added some in the back......probably the front because its less work JMO

2. jetting - when it stops pulling is it chopping up?, if so is it bad and if so is it starting about halfway through the gear? if so then try going bigger on the main to see if it gets any better

3. timing - if your timing if off one or 2 than it will also effect where the power goes (as mentioned previously).

I put these in order from easiest to hardest but I think its a good starting point before you start throwing good money after bad/ easy fixes :)

[katch26]

how many disk are in you WB pipe? r what kinf od end is on it now? if its wide open I wouldnt think it to be the pipe if youre using disks with the closed endcap too few a disks will really choke it up

you guys obviously know more about a 400ex engine than I do so Im not trying to step on toes but just thinking if we cover all the basics first we might get to the answer faster.

[400exrider707]

Lightened flywheel will make it slower, trust me, its a 400ex trait.

A cam will add lots of power. You're doing a lot of things with a cam, changing the valve timing, the duration the valves are open for, how far they open... a cam can do a lot for you if you know what you want.


Trust me my 400ex got spanked all the time by a stock 300ex. Both riders were equal in weight, I did have larger/heavier rear tires. In the sand I could just not keep up with it for whatever reason. It could be the motor was just old and tired. We were both virtually stock 400ex/300ex and same weight/riding level.

Originally posted by 400exrider707
Trust me my 400ex got spanked all the time by a stock 300ex. Both riders were equal in weight, I did have larger/heavier rear tires. In the sand I could just not keep up with it for whatever reason. It could be the motor was just old and tired. We were both virtually stock 400ex/300ex and same weight/riding level.

that means the 300ex rider was a better rider than you. no way should a stock vs stock race a 300ex win unless you arent so good at riding. Your motor would really have to be old to lose to one.

[katch26]

Originally posted by 400exrider707

A cam will add lots of power. You're doing a lot of things with a cam, changing the valve timing, the duration the valves are open for, how far they open... a cam can do a lot for you if you know what you want.


no youre right it will on a modified motor. Itll allow the more efficient use of other aftermarket parts, but on a stock machine youre talking 1-2 hp and that isnt going to help him beat a 300ex if he isnt already....something else is going on and I dont think its necessarily that the motor is "tired"

if both are stock you need to learn to ride better. covering up not so good riding with more power doesnt always mean you will win. a lot of 450 or banshee riders just plain suck. they only have the 450 or banshee because the extra power is a way to try and compensate and they think thats the only way they can compete. learn the quad more until you can beat a stock 300ex then try modding it so you flat out murder it

Originally posted by FoxHondaRider
if both are stock you need to learn to ride better. covering up not so good riding with more power doesnt always mean you will win. a lot of 450 or banshee riders just plain suck. they only have the 450 or banshee because the extra power is a way to try and compensate and they think thats the only way they can compete. learn the quad more until you can beat a stock 300ex then try modding it so you flat out murder it

omg if you said that on the banshee site you would be torn apart.

lol. While what you said may be true, you'd be surprised how many people actually do know about this stuff. I dont think theres one guy on bansheehq that bought one to make up for skill, they all are pretty good and smart.
Same goes for the 450 sites.

[UNBROKEN]

Originally posted by DMC-4OOEX
omg if you said that on the banshee site you would be torn apart.

lol. While what you said may be true, you'd be surprised how many people actually do know about this stuff. I dont think theres one guy on bansheehq that bought one to make up for skill, they all are pretty good and smart.
Same goes for the 450 sites.

lol is someone mad cuz they ride a banshee :D

Originally posted by UNBROKEN
lol is someone mad cuz they ride a banshee :D

lol, i could care less about what he said. I know how I ride.
But i was saying he said it almost like most people with 450's and banshee's dont know how to ride, when the majority of people do only a few select people do what he mentioned.

[trailrider894]

it isn't a skill issue that is causing it i know when something is just wrong. it has stock gearing in the motor and stock sprockets witch i got after purchasing it used. well i could add more plates to my pipe if that would help?? and yes it does have a closed end on it. well it just seems like after the 1/2 throttle you just don't feel that overwhelming power it just feels like the engine just doesn't have any go power!! i already have the lid off the air box and a k&n with outerwears. not sure what my carb is jetted to?? i prolly need to change it but seeing that it is winter here i don't wanna jet it and then have to change it again in a couple months to find out it doesn't solve the issue! could it be valve timing or something?? the 400ex is an 2000 and i haven't done much but just ride it so that may play a part. i have never adjusted the valve timing or stuff that like that.

[katch26]

so you said its been like this since you got it right, has it gotten better or worse since it got cold out? really until you look to see what your jetted at youre really going to be at a stand still because that is a high possibility. JMO
how many plates now?

[katch26]

an easy test would be to try putting the lid back on and see if its better or worse

[trailrider894]

i will check it out here in the next week and post back what it is. anyone know of the best way or precuations of taking the carb apart to look at it. my dad is a full time gm mechanic so i'll prolly have him help me. and how do i know what size the jet is?? does it say?

[trailrider894]

also the quad only goes 50mph?? is that hace anything to do with the issue??

[brian76708]

Originally posted by trailrider894
also the quad only goes 50mph?? is that hace anything to do with the issue??

yea thats not right you should be going at least mid to upper 60s. might be something wrong with your quad.

[trailrider894]

well then what would you guys say could be causing such an issue?? besides the carb witch i will taking a look at tommorow. and if so what all jetting would you recommend?? i have a kit jet already.

[BlasterEaten250]

Originally posted by DMC-4OOEX
lol, i could care less about what he said. I know how I ride.
But i was saying he said it almost like most people with 450's and banshee's dont know how to ride, when the majority of people do only a few select people do what he mentioned. I must say I have to agree with foxhondarider on this one. You have to realize that if someone is on a quad forum chances are they are serious about riding (good at it) But most 450 riders I see riding on the trails go fast in a strait line but that's about it

[brian76708]

Originally posted by trailrider894
well then what would you guys say could be causing such an issue?? besides the carb witch i will taking a look at tommorow. and if so what all jetting would you recommend?? i have a kit jet already.

well first off whats your gearing

[trailrider894]

i am almost sure it is stock. i have stock sprockets and the guy i bought it from never ever rode it and wasn't mechanicaly minded at all. and i have all the receipt of the work that was done on it sitting in front of me and there is no eninge work on it or gearing changes so i'm gonna say there is definetly not a gearing change.

[UNBROKEN]

how do we know it does 50mph ? have u had it clocked and if its got stock gearing it should do 60 mph easy

Originally posted by BlasterEaten250
I must say I have to agree with foxhondarider on this one. You have to realize that if someone is on a quad forum chances are they are serious about riding (good at it) But most 450 riders I see riding on the trails go fast in a strait line but that's about it

Well, you may be right. Maybe it's just the area I ride in, but at the coalmines and such there are a LOT of good riders. Almost every banshee there, they're climbing huge @ss hills. The 450 guys jumpin huge.

Only once have I ever seen someone REALLY not handle a bike. Bunch of puertoricans without helmets. One on a banshee one on a yz80.. lets just say it was hilarious to watch:p

But back on subject..
When my buddy first got his blaster running, it was so rich it wouldn't even go past 1/2 throttle. We pulled the lid off to make it leaner and while still rich, what a difference.

Im guessing maybe it's running way too rich on the main.
Try pulling the airbox lid off. if its still bad but better, put more disks in the exhaust to lean it up even more.

[trailrider894]

the lid is off was from the minute i got home i put the filter on it and took the id off then and there jetted it and the whole deal. but things change out here like my jetting i can never seem to get it just right.

[witech]

Kind of sounds like your cam timing might be a tooth advanced.

[trailrider894]

so then what all should i do as like maintenance or adjustments to maybe help with this issue??

[katch26]

Originally posted by katch26


this is what I would check
1. gearing - not sure if you bought it new or used but if its used than the previous owner may have wanted more down low grunt and either dropped a tooth (or teeth ) in the front or added some in the back......probably the front because its less work JMO

you said it had stock sprockets so we’re going with that

2. jetting - when it stops pulling is it chopping up?, (like youre hitting the rev limiter) if so is it bad and if so is it starting about halfway through the gear? if so then try going bigger on the main to see if it gets any better

3. timing - if your timing if off one or 2 than it will also effect where the power goes (as mentioned previously).

I put these in order from easiest to hardest but I think its a good starting point before you start throwing good money after bad/ easy fixes


not to beat a deadhorse or anything but at some point you're going to have to troubleshoot some of the ideas that people are throwing out and as more information is presented more people will be able to "steer" you in the right direction but you will need to pick a wrench up and give it a shot or if you don;t feel comfortable take it somewhere. The majority of suggestions are free and reversible. The open up the bottom of the carb and check out your main (write it down) and try some jets either side of it and if it helps or hurts at the point where its stumbling now. If that gets you nowhere put it back to the way it was no harm no foul and move on down the list.

[odog]

if u cant beat a 300ex then something is seriously wrong especially if both of them are stock the first thing i would do is check the gearing if the bike isnt smoking or riding bad and if ur only going 50mph u must have like a 13 tooth front sprocket and a 42 rear a bone stock 400 should be running mid to high 60s worse case scernio take it to your local honda dealer or local atv repair shop and have them check it and even if u had that low of a gearing u would be so fast out the hole and in the lower gears u would have to go about a quarter or half of mile before he would be able to catch up to you