power

[trx400ex07rider]

i recently purchased a 400ex, put a full hmf on it and have the air lid off but its still not enough power!!!!!! can any1 advise me on whats best if i want a ton of power and speed? should have gotten a 450r but u no how moms are.............

the pic is before the pipe as ull c

[MidnightBlade]

before you do anyhting up the main jet to a 153 or 154 the 158 is what came stock in my 05 put on a slip on and 153 main jet and got lots of power with some speed also you might want to go with a 155 because of the twin intake and no lid

[John Noftsinger]

YES !

[storms400ex]

you mean 148 is stock not 158 LOL

[MidnightBlade]

yeah that darn 4 and 5 are so close together and its dark in here lol

[trx400ex07rider]

I put a 155 in it and i dont think it's enough so i'm moving it to a 160 2marro. any other ideas? choke removal? I don't have money for 416, 426, or 440 kits but i need other cheaper things to do

[Miami_Vice454]

sparks timing advance key

[trx400ex07rider]

where can i get 1? and how much? installation?

[slightlybent47]

If you don’t have all you ridding gear that needs to be first on the list. Not saying your new but I hate to see a new rider who gets a new bike and wants to spend there money making it go faster before they even have a helmet. I’m not saying your one of those I’m just trying to let you know how important it is to be safe. These include helmet, boots chest protector, neck brace, and goggles. I see a lot of riders take there goggles off when they get dirty and still keep ridding. One rock and your blind for life.

If all that’s in order then save your money and do the whole upgread at one time. Like bore, cam, port & polish. These mods need to be done together, for one you’ll only have to go into the motor one time. And two these mods work together and if not done one at a time you wont feel much deference when you add something just by itself.

If you are a new rider then just ride it like it is, and get your ridding gear first. That ex has way more power and ability then you are giving it credit for.

The suspension is the weakest link on the ex, it has more motor then suspension.

Gear first – for safety
Suspension second – weakest link
Motor last – hold that throttle open and leave it there, it will go fast.

[MidnightBlade]

for all the more mods you got 160 would be WAY overkill i had a 158 in mine and it ran like a sack of crap go with a 156 or 157 then and do a plug chop get several times if you sont know get it up to about 4th gear wound out pretty good then squeeze the clutch and hit the kill switch at the same time then pull the plug out and see what color it is if its black jet it down if its tan its good abut if it white jet it up

[trx400ex07rider]

i have all the gear, don't worry and ive been riding since i was 4. ive had it WOT(wide open throttle) on a straight away road for about a half mile and even with my mods right now.......... it still doesnt feel like its getting much over 65mph. thanks for the help, 450r shocks and wider a arms would be nice lol i need to purchase more jets, mine skip from 155 to 160, nothin in between. oh so thats how you do the spark plug test, i did it b4 and it took a while for it to show its true color

[trx400ex07rider]

another question, is there a way to make my 400ex a kick instead of electric start? that could add some power also. rev boxes? sprockets?

and not to get off topic but covering my air box........ ive heard so many different ways that idk what is really the best, help?

[99exrider]

Ive been lurking the forums for the last month, Ive noticed a couple little minor budget upgrades that sound like they can help (Im in the same exact boat, want to go 416, but dad is way against messing with the bulletproof 400 motor)

Ive heard that a Sparks Ignition Advance Key is a VERY big upgrade for the stock motor, and is very cheap (15$) if im not mistaken.

depending on where you find one, a stock 450r carb would net you some extra horsepower.

I haven't read too much on rev boxes or gearing though enough to say what is effective.

If you want an overview of building a 416 tho, Ive priced mine at about $400 total, not including labor, and it is best to do engine upgrades all at once, because you dont want to have to go back in there a second time.

[trx400ex07rider]

ya, my dad is totally against any mods at all lol he got pissed when i got a pipe and rejetted it myself. only thing is idk how to install the key, 15 bucks is good but installation could mean takin it down to the shop etc. If i can get a 450r carb for cheap ill get it 4 sure. o ya ill take the over view for sure!!!

anyone know about changing from electric into kick?

[slightlybent47]

I’m glad you have the gear, that’s great, now I would do the suspension next, 450 shocks up front, +2 a arms and +4 axel will do wonders for it. The rear shock will hold up to some pretty big jumps and do well in the woops like it is. You make it wider and it will let you use more of the power that you already have. The ex is not a speed demon and doesn’t have a real good top end compared to a 450. It’s ability to give you good low and mid power with a predictable and useable throttle response is what makes it so great.

Why in the world would you want to make it a kick start? The electric start is one of the best things about the quad. There’s no better way of starting or restarting one then with a push of a button. If I stall in a corner I can usually get it cranked back up before I lose any speed to speak of. You almost have to stop with a kick start and in most cases you do. Meanwhile you’re getting hammered from behind because you can’t get going.
The amount of weight you save is not worth it not to mention that being very expensive if it could even be done. Put that money on the suspension and you won’t be sorry.

I got way faster after I did my suspension, I could get in and out of the corners faster which would let me get a better run at the next jump, and in turn I could then clear the jump. Giving you more speed and that will get you in rhythm with the track and that will let you go faster.

If you have a better suspension you will have more control over the bike. And better control will let you be faster. Not to mention that good shocks will let you keep it on the ground and get more traction.



Yes after you do the suspension you’ll want more power but one thing at a time, unless you are able to do them all now, then if that’s the case then let’s get busy.


Just my .02

[ish416]

trx400ex07rider, you mention that on a straight half mile of road it doesn't seem to hit much more than 65mph.

If you are looking for more top speed change the sprockets or get a larger rear tire. Either go up 1 in the front or down a few in the back. That will get your top speed up a little bit while sacrificing acceleration.

Don't expect to get any type of impressive gains without opening up the engine. Even with your mods, and the sparks timing key you are probably only gaining maybe 4 or 5hp at most. You might add 1.5hp with an FCR carb from a 450r but I wouldn't get your hopes up. You will most likely only notice the improved throttle response.

The most noticeable gains are going to be from a high compression, big bore piston (416 or 426) a cam and port and polish. With those mods plus the mods you already have you would probably be looking at somewhere around an 8hp gain over a stock 400ex.

With those mods you should be able to run with stock 450s and get away with running taller rear tires or changing the gearing without sacrificing much acceleration.

[bkelley]

It depends. I've seen a dyno slip where a 426 with a stage 2 cam, mild p&p, 450r carb (42mm) and an open air system put down 41 HP. That's about a 14HP increase over stock. That's where I'm hoping to be in a few months. A 42mm 450r carb and an open air system alone can net you a modest 5-6HP.

Here are the dynos from the 426 I was talking about.

http://img40.imageshack.us/img40/9709/dyno2.th.jpg (http://img40.imageshack.us/i/dyno2.jpg/)
http://img197.imageshack.us/img197/8029/dyno1q.th.jpg (http://img197.imageshack.us/i/dyno1q.jpg/)

[Ryan'07400ex]

The sparks key will make you feel like your going faster at first but then you won't notice you have it, unless you ride a 400 without one. Anyway you can get the actual key for 20 and then you need a flywheel puller bolt for about 10. Once you take the case off you will probably need a new gasket which for me was 17 dollars. I think a 15 tooth sprocket is a good idea to its cheap as well (15 bucks) and will give you a bit more speed. The accel. you lose you'll get back and surpass with the 6* key.


you were saying you don't want to take it to a shop, you won't it is easy if you follow this thread made by tri5ron

http://www.exriders.com/vbb/showthread.php?s=&threadid=349499&highlight=Sparks+timing+and+degree

[bigbad400]

first off you are doing the jetting backwards. you always start with a bigger jet than you need and run it wot and look for a stumble in the top, then lower the jets untill the stumble goes away. by going up one at a time your making it run lean and probably causing alot of heat. a little rich is always better than lean.

second, there is no reason a cam would be detrimental to the reliability of the motor and your not even into the motor really. relatively cheap power gain. another is a 450r carb. there again no reason it would make it less reliable unless you messed up jetting it. decent little gain too.

third, changing from electric start to a kicker wont be noticable in power increase. its like 4 lbs of weight thats it. take a crap befor you ride and youll be good. its too much of a pain to get rid of that if you dont have to. your dad was mad that you put a pipe on the wheeler your not gonna get away with a timing key a cam and a carb. but just so you know, the sparks key comes with a flywheel puller. its 30 shipped for the key and the puller. good little gain.

stay away from cdis the 400ex makes its power in the lower part of the rpm range. all a cdi will do is alow you to over rev it and blow it up. if you want something to help get a monster coil, it just increases spark energy and makes it burn more efficiently and clean. easier starting too i think.

good luck i hope i helped some.

[slightlybent47]

Putting a 450 carb won’t do much of anything without a port and polish, cam and a pipe and slip on to go with it. Remember if the air wont flow out any faster a bigger carb wont make it go in any faster. They work together, so that’s why I suggest you do them all at one time.
The bore, compression, cam, P & P, carb must all work together to get you any real gains in hp. There all good mods but it’s best to do these all at one time. It saves time and money. You should be able to get all of them done for around $1000.00 – 1500.00 depending on who dose the work. That’s parts and labor.

[trx400ex07rider]

I'm deff. gonna go with the 450r suspension and +2 a arms and a +4 axle, but all that is pretty $$$ for what i have right now but i'm working on it. Scratch the kick start then lol I'm looking at the 416, and 426 kits but i'm concerned with over heating problems(more reason 4 the pops to yell at me) I deff. want to keep up with the 450's, thats my goal. what exactly is the port and polish u guys r talking about? I'm gonna try a sprocket 4 sure, nice and cheap for the gains and the sparks key. bigbad400, ur right, i figured going from 142 stock to 150 would be enough with my mods but i know now it isnt now. as of right now, i dont have 1000-1500 bucks to throw around but as i said i'm working on it. im gonna save up and do them all at once.

[jasonwayne222]

ok first off it must be nice to have mommy and daddy buy u a brand new quad

second, dont go boring that thing just yet, you will get plenty more power by keeping the stock bore and throwing in a high compression piston, I would suggest 11:1 comp. and a stage 2 cam, this way you have plenty of room for rebuilds in the future.
While you are in there I would put in a CRF 450 timing chain.

And running a 160 jet on a stock machine with just a pipe is probly too rich, pull your plug and check the color, if its black and wet you need to go down on your main.

[slightlybent47]

Look for some used parts for the suspension. My a arms and tie rods 450 shocks the elka on the rear, and the + 4 axel are all use parts and have worked well and have held up to two years of racing and still going strong.
I got all of from other members in my racing community and I paid less then half of what it would have been new.
I have a lone star double roller carrier for the rear for sale, if you want it I’ll let go for $100.00 plus shipping.
I did my suspension first and I have no regrets on doing it, like I said before with a better suspension you can attack the track with more confidence and be able to soke up the bumps much better. That alone will let you go faster. All tracks will have a rhythm to them and if you can get up to that speed you will flow with the track and that will make you faster. If you fighting the bike and the track it will slow you down.

Trust me the motor has more power then the suspension will allow it to go.

[slightlybent47]

A p&p. The intake ports on the head are ground down and cut away to allow more air flow thorough the head. The exhaust port is not ground much but it polished so the exhaust gasses can escape faster. This allows more air to flow through the head and in turn makes more power. There are two ways to do a p&p, one called a recreational p&p and is less aggressive in the amount of material that is removed from the ports. The other is a race p&p and will take as much material out as can be tolerated and still hold together. A gas motor is just a big air pump and the more air flow you can get through it the better.
That’s why you do all the mods together. You can put a bigger carb on it, but without the ability for all that extra air and fuel to escape you are just wasting your time.

I hope that helps.

[trx400ex07rider]

i paid for the quad, worked for 3 summers all summer and i finally got it lol ya i tested the plug today and the 160 is to rich by a hair and the 155 is a hair lean, ill get a better dyno jet kit.

so boreing it out can cause problems?

good idea on the used parts, ill be looking around. what width is the lonestar axle compared to stock?

Thanks for all the info on the p&p, ill deff. be doing that

[clemsonteg]

Just in case you don't already have it here are the recommendations for dynojet jets. This obviously just a starting point but usually when people quote jets on the forum they don't base it on dynojet numbers they do it on keihn numbers and they don't exactly match up. I also saw you said you went from the factory 142 to a 150, factory should have been a 148 keihn jet not a 142.

http://www.dynojet.com/pdf/Q107.pdf

[slightlybent47]

No boring won’t cause any problems if done correctly. Up to a 416 – 426 is fine and the HD studs are not required, again if the head studs are torque properly then it will be fine.
Anything over that and heating, and head gaskets can start to give you problems. But again this all depends on the quality of the work. You can increase the compression up 12-1 and still theoretically run 93 pump gas. Anything over 12-1 and race gas is a must.
I have a 416 with 12-1 je piston, stage 2 cam, oversized oil tank, recreational p&p, wb pipe and 450 carb. And it runs great… and I have run the piss out of it.

Remember to get the best qualified person to work on it. Some back yard mechanics don’t know how or cut corners and don’t do the best work.

I still think the suspension will be your next best move. But it never too soon to talk about the motor and what you want to do. Research is your best tool.
If you want a flat out speed bike the ex is not going to do that for you, no mater what mods you do. But for an all around great track and woods bike thats dependable and easy to ride and control, the ex is hard to beat.

[Ryan'07400ex]

This is off topic sorry but if you port and polish you gas mileage will suffer wont it? May be completely wrong but idk. Sorry to jack your thread btw


A SPAL fan for 30 bucks helps cool everything

[slightlybent47]

Originally posted by Ryan'07400ex
This is off topic sorry but if you port and polish you gas mileage will suffer wont it? May be completely wrong but idk. Sorry to jack your thread btw


A SPAL fan for 30 bucks helps cool everything

Actually I think it get better mileage now. I have no evidence or proof but it just seems like I use less.

[99exrider]

Originally posted by slightlybent47
Actually I think it get better mileage now. I have no evidence or proof but it just seems like I use less.


lucky you... I rip mine WOT through the dunes, and it seems like im going threw a tank every 5 hours (on a pretty much nonstop weekend)

I wanted to chime back in on the heating issue, I really dont know much about the SPAL fans. Ive heard that they requre a bit of fabbing to fit in no? and dont you have to relocate the oil tank?

But from what ive read, there havent been reports of overheating with a 416 or 426, but once you move to the 440's, thats when you NEED cooling.

If you were really worried about a 416 heating, I would either get the fan, or slap on a pair of radiator foils. there pretty cheap too.

[Forest]

get on the curtis sparks web page and pull out your credit card........lol

[Ryan'07400ex]

Originally posted by 99exrider

I wanted to chime back in on the heating issue, I really dont know much about the SPAL fans. Ive heard that they requre a bit of fabbing to fit in no? and dont you have to relocate the oil tank?


I cut the "heat shield" between the engine and gas tank a little, about 3 inches only, and found little strips of steel to mount it to the "radiator" with. I didn't have to move anything like a oil tank though. Of course you have to run wiring to some power source and I put a fuse on it.

My 400 is stock but I just liked the idea of running cooler anyway.

The easy time to do it would be next time you jet it and take the plastic and tank off. You could reach everything easier

[99exrider]

Originally posted by Ryan'07400ex
I cut the "heat shield" between the engine and gas tank a little, about 3 inches only, and found little strips of steel to mount it to the "radiator" with. I didn't have to move anything like a oil tank though. Of course you have to run wiring to some power source and I put a fuse on it.

My 400 is stock but I just liked the idea of running cooler anyway.

The easy time to do it would be next time you jet it and take the plastic and tank off. You could reach everything easier


Thanks for the info! Ill have to look into that then, I thought the idea of having a small fan on there would be perfect for when im running hot in the desert.

[trx400ex07rider]

good, i'm deff. gonna bore it to a 416 or 426 when i get the $ but the suspension will be first. I'll have my local shop do the work.

Any1 have used 450r shocks they wanna sell?

The ex was basically my only option to get though slightly47bent, wouldnt lemme get a 450r and i had to have a honda cuz thats who my dad likes and he wont budge. so i was stuck. what exactly is a SPAL fan?

[trx400ex07rider]

and i meant changed the stock 148* jet to the 155 not 142 to 150, my b

[slightlybent47]

Originally posted by trx400ex07rider
good, i'm deff. gonna bore it to a 416 or 426 when i get the $ but the suspension will be first. I'll have my local shop do the work.

Any1 have used 450r shocks they wanna sell?

The ex was basically my only option to get though slightly47bent, wouldnt lemme get a 450r and i had to have a honda cuz thats who my dad likes and he wont budge. so i was stuck. what exactly is a SPAL fan?


Since all you have at the moment is a full pipe and the lid off the air breather then I would think you would only have to change the main jet one or two numbers at most to put you where you need to be. The changes you’ve done probably haven’t affected the fuel mixture much so you’re probably close anyway.

Don’t be so quick to put down a Honda or the ex just because it’s not a 450.
That’s a great bike and Honda makes some good stuff.

Keep an eye out on the “for sale section” for your parts, and you can do the suspension work your self. Basic tools are all you need.

[Ryan'07400ex]

Originally posted by trx400ex07rider

i had to have a honda cuz thats who my dad likes and he wont budge. so i was stuck. what exactly is a SPAL fan?

Smart man.....

Its a little fan that comes in 4 inches diameter (or bigger) that is supposed to be good for outdoors cause the motor is internal/water tight. SPAL is the brand i guess haha

110 for a kit seems expensive but idk.


And I can't get the links to work but go to ebay type "SPAL 4' "

[clemsonteg]

Originally posted by trx400ex07rider
and i meant changed the stock 148* jet to the 155 not 142 to 150, my b

What type of jets did you use? Your sig says dyno jets but then you list the main jet again. Wasn't sure what you were using.

[honda400ex2003]

sounds to me like you are asking too much out of a 400. lol. ride it for what it is not what it should be. lol. you will not be getting good gas mileage with a 450 carb, 416, and a cam. you will go from 40+ to 30 or less with a 450 carb. i havent got to ride mine yet to see what it is at with the new carb. otherwise, put a 158 in it leave the needle alone, 3 turns out on the f/a screw and you should be pretty good, (dont forget the dynojets are a different size if you are still using them. you should be right around a 142 if you have a dynojet in it), get the sparks key, put a 15/38 combo on it, monster coil, arms, shocks, axle. if you still dont like it then you can go to a 406 or 416 relatively easy. 10-11:1 would both be nice. I love my 10:1, it keeps up with any 11:1 i have ridden with and can sometimes outrun them. sounds like you have it under control after the 4 pages i just read. steve

[trx400ex07rider]

slightlybent47, ya im just doin the main jet for now. ya i do have 2 say honda makes the most dependable stuff for sure!!!! thanks ill keep an eye on it.

well if 110$ keeps my engine cool then ill take it lol

the jet package is fmf jet kit, idk what kinda jet the measurement is but i no it works lol

ya i think i am but dad wouldnt get me bigger than a 400 cuz he knows im crazy. eh, gas $ isnt a big issue 4 me lol ill take the power.

steve, whats a 15/38 combo? think i have it under control for not knowing anything bout how a quad works 3 months ago lol all self taught by taking my old 250ex apart.

[honda400ex2003]

front and rear gears. lol. steve

[slightlybent47]

Originally posted by trx400ex07rider
slightlybent47, ya im just doin the main jet for now. ya i do have 2 say honda makes the most dependable stuff for sure!!!! thanks ill keep an eye on it.

well if 110$ keeps my engine cool then ill take it lol

the jet package is fmf jet kit, idk what kinda jet the measurement is but i no it works lol

ya i think i am but dad wouldnt get me bigger than a 400 cuz he knows im crazy. eh, gas $ isnt a big issue 4 me lol ill take the power.

steve, whats a 15/38 combo? think i have it under control for not knowing anything bout how a quad works 3 months ago lol all self taught by taking my old 250ex apart.



The next challenge since you took apart the 250, is to put it back together and make it run. I’m sure that 250 gave you many hours of riding fun so respect the old girl and put her back together. You should not be having any overheating issues with that let say stock ex. The mods you have done should not be making it run hot.



Like steve said just enjoy it for what it is.

And remember sometimes you have to slow down in order to go fast.
Read my sig.

[trx400ex07rider]

gotcha. oh i put the 250 bak together a while ago, i loved that lil bike lol hundreds of hours of riding on it.

slow down in order to go fast.......... ill keep that in mind, my quote is floor it lol im the guy who wil take 1st place or crash trying

[Rscarpantonio]

not sure if it was mentioned here already or not but by advancing the timing on an engine you make it run hotter, atleast with outboard motors, im assuming its the same for most any motor (4 stroke) i never looked into it much at all on this site about doing it to my quad but usualy when we rebuild the outboards we retard the timing a couple of degrees and for each degree you retard it it cools the engine about 15 percent or so.
just my .02 on it and something to think about. such as over heating issues

[honda400ex2003]

very good info on retarding the timing. it does make more heat in the 400 motors to advance the timing. I would say on average it is around 15-20 degrees depending on setup with a 6 degree. it is about 10 degrees with the 3 degree from wheelie. steve

[trx400ex07rider]

the over heating is the only thing i dont like about the advanced timing key and the boreing, makin it a 426 or 440, both of which can cause over heating problems

[honda400ex2003]

the key is not going to make enough difference to make it over heat without it being a 440 or something with 11:1 comp or 12:1. you would have to let it run for quite a while sitting still before it would overheat. run premium in it and you will be fine. steve