rebuild time!

[hondaking52]

hey guys, haven't been on here in a while. to busy with sledding! haha. but i think its time to do the top end on my 400. did a comp test and I'm down to 88psi. I'm not even sure what the norm is but its gotta be above 100, not smoking yet though. but anyways i was thinking a 416 and a cam, but i was reading i have to get the cyl bored for a 416? could i keep the stock bore and put a higher comp piston in it? or should i just get it bored and go with a 416? just looking for some opinions.

thanks guys

[CJM]

100-120 is normal iirc

416 is a larger piston, you would have to bore it out. But by now if you have tons of hours on the quad the cylinder might not be round anymore and might be part of the reason (or the reason itself) your losing compression b/c the rings arent sealing-although you would be getting smoke in most cases.

Make sure your not getting a false reading for compression test and your gauge is accurate too just to save your self unneeded work.


You can keep the stock bore andput a high compression piston in-but like i said earlier; the cylinder might be out of round and need a bore anyways.

416 is a best bet,piston and boring it all will run you about 200 bucks and the place thats boringit will need the piston to do the job properly. And if your doing all that its time for a hotcam, some cometic brand gaskets and a new timing chain, chain tensioner and guides as well as a valve adjustment and checking the valve springs to be sure they are inspec and thenlapping and cleaningup the valves.

It seems like alot of work, but it reallyisnt and everyone here canhelp you do it if you ask.

[killer454]

if you just put a new piston in it their is allways a chance the cylinder is woreout and you just wasted money on a std piston.

i always boreout the cylinder and buy a piston to match,i did my 00 400ex a few months ago.i went with a .020 overbore and a stage1 hotcam and it had a pro cuircuit pipe already.

you can see the video on youtube
do a search (400ex first startup)

this thing rocks with a 11-1 piston and the cam

if you have alot of hours on this atv i would bore it out,most shops only charge 50-60.00 to do it.

[hondaking52]

ya its almost 10 years old so it could very well be out of round now. i was gonna do a cam either way, probably a stg 1 HC. I'll probably take it to bondi engines and have him do the boring and have him do the valve seals and regrind them if they need it. its def getting a cometic gasket kit.
i've got the valve cover off now, probably have the cyl off tomorrow night and we'll see how she looks. best place for a 416 kit?

[CJM]

JE or wiseco, I got mine of ebay it was a wiseco 416 kit for like 120.

if your gonna do 416 you have a choice between the cams but stage 2 will work much better inthat engine than a stage 1. stage 2 will give you all aorund gains and a good mid to top end, stage 1 cuts out to low.

make sure you replace all theother junk i listed when you got it apart, also check your clutch plates out too, this is the time to go over with a fine tooth comb and make sure you wont have any issues for a long time.

[hondaking52]

ok i'll have to have a look on ebay. and i'm not sure about a stg 2, heard its more for top end gains

[CJM]

it is, but in my expierance with the right gearing it will make you a very happy rider. you wil have the lowend with the right gearing (14/38, stocks 15/38) piston and its compression, and the topend with the cam. I love mine. I can pull on mildly worked 450s and keep up with most everything else besides those insane ktms easy,

[hondaking52]

hmm, never thought of dropping a tooth...

[hondaking52]

well i got it all tore apart tonight, actually looks very good for its age!, got my parts list goin with colby
416 kit(10.1)
gasket set
hc stg 2
Hd timing chain

[NacsMXer]

I'd go 11:1 on the compression, especially if you are getting the Stage 2 Hotcam. You might loose too much compression if you mate a larger cam with less compression. I used to have a 10:1 440 and it wasn't super impressive. Stock is 9.5:1 so half a compression point more to 10:1 isn't much of a change.

[hondaking52]

even if i have the sparks key?

[finsteratv]

when i looked it up i saw it was 9:1 stock?
400's also lose about .5 from one of the certain gaskets or somthing like that??
if you really dont feel safe with 11:1 you can always go 10.5:1 or 10.8:1 haha

[NacsMXer]

Originally posted by finsteratv
when i looked it up i saw it was 9:1 stock?
400's also lose about .5 from one of the certain gaskets or somthing like that??
if you really dont feel safe with 11:1 you can always go 10.5:1 or 10.8:1 haha

Doh, i'm not remembering correctly, you are right. Stock compression ratio is 9.1:1.

And i've never ran a Sparks key, so I couldn't tell you. You could also consider an 11:1 setup with one of Wheelie's milder +3 timing keys if it's the timing of the Sparks key that's holding you back.

[hondaking52]

Ya I just thought the key would would make up for the lack of the 11.1 compression, because I'm pretty sure they say not to run over 11.1 with the key

[CJM]

Run 11:1 with the key and you need 100+ octane to prevent detonation (pinging).

Key usually makes up for the lack of compression. Still, its all in how you wanna do it. Spend the 20 bucks for the key and puller and buy the gasket (its like 10 bucks iirc) and do 10:1 or 10:8 (harder to find those odd comp ratios) or no key, save yourself a few bucks and do 11:1.

I think its all apples to apples here, what you do gain is a good bump over stock compression with the 11:1 vs the 10:1 tho.

Im quite happy with my setup, just had to find the right gearing and its quite good for me. I ride in sand pits and trails usually very fast. I like the way the 416 revs and the way the 11:1 helps it get there.

[sheweezy]

What it be a pointless mod or would i be unable to run the sparks key with a 406 bore and 10:1 compression

[hondaking52]

ya the thing is i already have the key in it, so should i run 10.1 with the key? or take it out and run 11.1?

[CJM]

Originally posted by hondaking52
ya the thing is i already have the key in it, so should i run 10.1 with the key? or take it out and run 11.1?

Your call really. Id leave the key and do 10:1. It gives it a little boost over just the higher compression alone.

[finsteratv]

shouldnt also run a little cooler/more reliable being at a lower compression?

[Pabst_Powered]

Hondaking52, thanx for asking this, I'm in the same boat, when I checked my PSI it was still at 118 but I would like to rebuild anyway for power, I also have the key and lookin what I may do, 10:1 416, 426, 440, or a 11:1 416, 426, and a cam, I mostly would like to be able to run 93 still, i'll be watchin this

[CJM]

Yes it should run slightly cooler with the lower comp. You negate most of the cooler temps with the key tho I think.

If I had to do it all over I think I would try 10:1 and the key just to see what its like.

[hondaking52]

ya i think thats what i'm going to do, talkin with colby about it also

[hondaking52]

little update, got all the parts, cyl is bored. just starting to put it all together! just trying to figure out what i need to do to the carb....it seems most guys run around a 165-175 main and a 42 pilot, 3rd or 4th clip down? now all my dyno jet kit has is mains, so i was just wondering were you get pilots from or if you guys had a honda part number? cause i know my parts lady is just gonna look at me funny...haha. but what do you guys think my jetting should be? 11.1 416, HC stage 2, stock header with mod/hmf slip-on and a k&n filter lid on.

thanks again

[CJM]

You can buy any jet you want from www.jetsrus.com. They sell pilots, main jets and other carb parts.

Im gonna guess, that depending on your elevation: 165-172 main, needle 2nd or 3rd clip and 42 pilot.

Im close to sea level and have a 416, open airbox, cam, etc and run a 170, 42 pilot, 3rd clip and 2.75 turns out the air/fuel screw.

Buy an assortment of jets and see where they take ya. I have every size from stock to 200 just because lol

[hondaking52]

haha, ya i think i'm sniffing right around 250ft give or take. i'll have to check them out and get them up here asap! thanks man! do you know if the honda dealer can get them though?

[CJM]

They can get them or might have them in stock. Depends on the dealer. Might even try calling up other powersports dealers and telling them the jet numbers you want as alot of quads use similar jets.

Key to these carbs is to only use keihin jets (oem) and not dynojets or something else. They run best with OEM.

[hondaking52]

ok sounds good, i have to go there tomorrow to pick up some gaskets so i'll have them check and see what they can get. thanks again

[hondaking52]

also, if you say the stock carb likes keihin jets should i put the stock needle back in also? or can i run the dyno jet needle with the shim?

[CJM]

Go back to the stock needle.

I tried the DJ and they do work, but when I finally switched out I got totally rid of the crappy bog I had with the DJ. Stock are also much more precise imho than the DJ's.

[hondaking52]

well i've got it together to the point i can start it, problem is now it wont stay running, pops and fires, ran for about 10 secs a couple times...gonna go back out and tinker with it, do the check list..running a 165 main and a 42 pilot, lid on. any idea's would be great! thanks

[CJM]

Are you still using the DJ mains or did you get some keihins?

You probably should try a 172 keihin main to start with, 42 pilot, 2.5 turns out the air/fuel screw.

If it wont stay running check to make sure its getting gas and if the floats working properly. had the same issue on a YZF450 about 3 weeks ago-float needle was stuck, once we fixed that-was fine.

[hondaking52]

Starts and runs fine now, just won't idle...

[ridehonda400ex]

Turn up idle screw or mess with f/a screw

[CJM]

Yes, adjust the idle screw a bit.

For me, I need to have the idle slightly turned up period or it wont stay running. When it finally does warm up it needs to be turned down slightly depending on how you want it.

[hondaking52]

runs mint now, forgot my choke was on...lol. rode it around for about 15min, gonna do another 15 in the morning, let it cool and check everything and change the oil, seems good so far though, ticks a bit so i'm gonna check my valves again.

[CJM]

Break it in like this: http://www.mototuneusa.com/break_in_secrets.htm

it works everytime, do not take it easy or the rings wont seat.

[hondaking52]

ya i was varying the throttle tonight, gonna run it hard tomorrow for 20min or so then do the checks and stuff

[hondaking52]

ok...so i'm either loosing my mind or something is fishy....lol, checked my plug this morning and it was running lean, bumped it up to a 170, still lean, played with the f/a screw, nothing, bumped it up to a 178 and i cleaned the electrode so it was clean so i could get a fresh reading. run it around and its got a slight bog now and then(which i figured it would with a 178) pull the plug, still shiny new.......dropped back down to the 170.......still shiny......played with the f/a screw, nothing. then i put my old plug in which was brown , went for a boot and then i pulled it, still brown.... so idk why the new plug hasnt changed colors after i cleaned it and did all those jetting changes??? and now the old plug hasnt changed either....so is it running lean or what???? and each ride was about 10 min or so..

[hondaking52]

any idea's?