Callaing all experts to help with rebuild!

[Mustangous]

Hello All!
Unfortunately my buddies shifter shaft broke and we tore the whole motor apart and split the case. Now, the delema is, do we want the just replace the shifter shaft and put everything back together or we are thinking we should upgrade while we have everything apart? We are wanting to upgrade.

Just to let you know, we are not looking to make this like a high reving 450r! we still want a best trailable quad the 400ex was made for. Since most of you guys do this day in and day out i am looking for your opinions and guidance. I am looking for all details if possible.

The details is that its a 2004 400ex that was been very well maintained and has relatively low hours for its age. Its all stock. The only thing changed is the front tires. lol

So please let me know how I should process with up grades. I am looking For your guys guidance on this.

So what pistons, gaskets, rings, who should i send this to, or should i look local, ect.... Since most of you so this all the time i am looking for your expertise!

I dont do this ever day but i am capable of doing this rebuild. Please help! lol

[honda400ex2003]

you could do all of the bearings in the engine. that would be a good thing to do while in there. clean it good inside and check all of the tolerances on everything. do a cam chain, guides, do a valve lap, do a refresh on the piston just with a 416 imo. you could do a hd crank but i dont think it will be needed unless you do some more and radical stuff to it. that would be my starting stuff to do to it. steve

[Mustangous]

Originally posted by honda400ex2003
you could do all of the bearings in the engine. that would be a good thing to do while in there. clean it good inside and check all of the tolerances on everything. do a cam chain, guides, do a valve lap, do a refresh on the piston just with a 416 imo. you could do a hd crank but i dont think it will be needed unless you do some more and radical stuff to it. that would be my starting stuff to do to it. steve
Thanks for the start!

So what compression piston is good without running race mix fuel?

So what we are thinking is:
416 piston
hot cam stage 1
heavy duty head studs
crf timing chain
uni-air filter w/ ehs air box lid cover
450r carb
grind the welds in the header pipe

Heard a crf250 or 450's timing chain would be just as good as a heavy duty aftermarket timing chain but cheaper. anyone hear that?

Any suggestions for an exhaust that is not obnoxiously loud, but has good power gains?

Also thinking about sending the head out to get port and polished and a 3 angle valve job. Is it worth the cash and where is a good place to send it too?

will i need heavy duty valve springs?

[MidnightBlade]

id get a full yosh system or a white bros r4 or e series. i like my supertrapp but it is obnoxiuosly loud even with all the plates. yes the hd crf 450 timing chain is the best bet and one of the cheapest.

2x on what they said. also add a stage 2 h/c a 450r carb and p&p the head. and it will be a nice woods and mx quoad. look at my mods its a 440 and it holds up great. just look the video at how we dog it.
<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid825.photobucket.com%2Falbums% 2Fzz179%2Fericcrip%2Fmov01695.mp4"> sorry im not high jacking you.

[honda400ex2003]

put your vids away lol. if you want low end and mid get the stage 1, mid and top end stage 2. dont go by a video of some 400 to make a decision.

11:1 is usually safe on 93 octane in most cases. 1.5:1 would need race gas, 10:1 is 91 or higher will be fine. I like my t-4 but it is around 95 dBs. my q4 is around 90 dBs. 450 chains will work good also, the studs will be a good idea if you are going to go 11:1. sounds like a good combo you have listed previously. steve

the stage 2 (IS) the better cam with the 416 kit and you add the p&p head. thats where you realy get the power from with a 450r carb. then my friend you have a nice all around quad. ask any one that bield motors and thay will say with out a good head you have nothing.

sorry builds motors.

[honda400ex2003]

Originally posted by ericcrip
the stage 2 (IS) the better cam with the 416 kit and you add the p&p head. thats where you realy get the power from with a 450r carb. then my friend you have a nice all around quad. ask any one that bield motors and thay will say with out a good head you have nothing.

it will depend on how much compression it has and where wants the power to be. steve

so what your saying is the comp. make the hp ?that would be like saying i have a motor with 11.5.1 comp with a stage 1 will out run and have more power. than say your 10.1 comp. stage 1 with p&p head ? ask any one that builds motors and thay will say with out a good set of heads or head it only a lot of wasted comp. a good head is every thing no matter how you look at it .

[honda400ex2003]

yes that is exactly what i am saying. compression makes power not displacement. Im not talking about a head, i am talking about a cam. 2 different things. as you have seen as well as i have, more low end needs a smaller duration cam. simple as that. more top end, run a bigger duration cam. the higher the compression, the more adjustments you can make without losing too much dynamic compression. a few of you guys really dont know the slightest thing about engine internals. sorry to pop your bubble. no matter how fast it is, how fast you can go on a track, or anything... it doesnt matter if you dont understand how it is. coming from a mechanical engineer who knows quite a bit about the thermodynamic properties of internal combustion engines. more compression=more efficient. this isnt rocket science but it can seem like it. steve

[honda400ex2003]

for the op, if you go with a stage 1 cam and a 450 carb it is a great compromise of both if you go with 10:1 . 11:1 you could do stage 2 with a 450 carb and get about the same results compromise wise with some more hp to go with it. first you have to determine what comp you want to run before you go any further. steve

[Mustangous]

I was thing of going with a 10:1 because I would like to stay pump gas.

Is there anything I should do with timing? I have to read more but I remember talks about sparks timing key and cdl box??

I am still debating porting the head. Not sure if it's worth the 4-500 dollars. Than the other option of adding 1mm bigger valves, are all this worth the money?? I guess it is, but just not sure if I want to spend another $600 on top of all this.

I sent an email out to gt thunder about doing all the machine work, any opinions/ recommendations who else I should check out?

look go back to your lil world of talking like you know motors. that one that you need to study more on. a good flowing head is the trick to it all. i build car motors and bikes as well and with out a good head you have nothing. my son has a 350 punched 60 over with the same pistion that i have my 350 is punch 30 over same cam same set up other then the 60 over . we have the same set of heads 70 cc heads he has 194/1.5 valves stock heads mine are 70cc heads 202/1.6 p&p his motor on the dyno is 425hp my motor on the dyno 575hp im running 12.1 comp and hes at 12.5.1 i make more power becouse of the heads. so i not trying to jack you post . all so the p&p head is only $225 to get it done that what i payed and the vavels are $20 each on ebay so for 4 valves its $80 and i think c&d racing will do them for like $105 so all and all its $410 to do up the head i do not have the valve yet.

[honda400ex2003]

dude, calm down... heads and cams are totally different. a good flowing head is a contributing factor to the engine.. yes we all know that. congrats on making that revelation. you are saying that you can get more hp from an engine. ok... where your cams the same? I bet yours were a much bigger duration cam. How was the torque on both. I bet his was higher torque numbers at a given rpm compared to yours. you talk top end hp like you know about the total package. like i said, i really could give a darn about how fast something is or how much power it has total. numbers are numbers. it is how they perform that is what determines it. you should ask any engine builder which is better, torque or hp. any builder with a reputation will say both with emphisis on the torque since it gets you out of the hole faster. this is where the compression comes in. torque, not hp all the time. you run a 450 carb, stage 2 or 3, full pipe. all set up for top end. nothing low end there at all. get a slip on, stage 1, and a carb you have the torque numbers not the hp numbers. what you dont know is how an engine works completely. :rolleyes: we obviously arent talking about the same things here. steve

[honda400ex2003]

http://www.exriders.com/vbb/showthread.php?s=&threadid=237131&highlight=dynamic+compression

some good reading on choosing a cam to fit your wants and needs. steve

i see why we are not getting any where now. but what you was saying about comp is torque & torque is hp. yes it is but what is a lot hp a torque with out a good ( wait for it here it is CAM AND GOOD FLOWING HEAD a lot of nothing. you need all the parts to work well with each other. books help you yes but hands no win every time. there just some things you just cant get from a book. i worked for 10 year as a enginer in south florida for (us sugar). bye the way happy B-DAY 8-10-10 MINE IS 8-6-10 THIS IS WHY WE ARE NOT GOING TO GET ANY WHERE GO LEO'S LOL have a nice day.

[dalejiw25]

Whoa,Whoa,Whoa.... Can't we all just get along ??, You both need a time out. Now go ride your bikes. (In opposite directions)

[sc400ex_rider]

I would go 10:1 piston, stg 2 Hot cam and a sparks key. That would be a fun combo. you can add a 450 carb later. Open up the airbox add a filter. Open up the exhaust a little and it will rip. also you dont need a loud @ss pipe. i got 71.9 mph through the stock (modded for flow) Muffler. Also put the 450r timing chain in there while its apart. Make sure you retract the tensioner correctly before installing it or you will destroy it. Check the screen for the oil pump pickup at the bottom of the engine for debris. Look for metal chunks it will tell you the condition of the gears. Get a free online manual for torque specs those little 8 and 10MM only need 8-12 ft. lbs.

[honda400ex2003]

Originally posted by ericcrip
i see why we are not getting any where now. but what you was saying about comp is torque & torque is hp. yes it is but what is a lot hp a torque with out a good ( wait for it here it is CAM AND GOOD FLOWING HEAD a lot of nothing. you need all the parts to work well with each other. books help you yes but hands no win every time. there just some things you just cant get from a book. i worked for 10 year as a enginer in south florida for (us sugar). bye the way happy B-DAY 8-10-10 MINE IS 8-6-10 THIS IS WHY WE ARE NOT GOING TO GET ANY WHERE GO LEO'S LOL have a nice day.

see now we are coming around to where we both agree. it is everything together not just one part. the total package makes it. :D happy bday to you also. :D steve

[Mustangous]

ok, so after reading this has me a bit puzzled
http://www.exriders.com/vbb/showthread.php?threadid=239440
So if i go with the stage 2 cam, should i up the compression? If I up the compression could i still run on pump gas because through the duration and lift I will be loosing some compression, right?

[honda400ex2003]

what are you wanting to run? that is the question and where do you want your power to be at? I would suggest a compression bump with a stage 2 depending on the circumstances and wouldnt for others. lol steve

[Mustangous]

Originally posted by honda400ex2003
what are you wanting to run? that is the question and where do you want your power to be at? I would suggest a compression bump with a stage 2 depending on the circumstances and wouldnt for others. lol steve I will be running premium, but dont want any issues if the fuel gets a little old/stale. I want good mid range.

I am thinking about the 1mm bigger valves with porting and polishing. Would there be any reliability issues? Am i going too crazy?

[honda400ex2003]

you should be fine with oversize valves and such. get the stage 2 and go 11:1 and you will be happy for a long time. :D you will be able to run 93 all day and not have any issues with it. steve

now i agree with steve. and later do some p&p to the head.