rebuild

[400exBRAAP]

im going to be tearing into my 400ex engine today. is there anything i need to watch out for? and can someone give me some helpful step by step details on what i can do to make things go easier?

[nick249420]

take pictures

zip lock bags !
or tackle box to keep all the bolts in order
tag your parts
take notes ... thats bout all i would know

dont break anything :D

[400exBRAAP]

alrighty, and BTW folks, this aint my first engine or anything, ive rebuild 2 dirt bikes i think 3x each, and i helped my grandpa rebuild a tractor, so its not foreign to me, its just different cuz its a 4-stroke. and thanks for the quick reply. i will try that, never did it on dirt bikes, but i will give it a shot this time,

[maxfior]

For stubborn bolts, don't forget to use some heat!

M.

[underpowered]

to me it is simple. take bolts out, put them back in reverse order. an engine is and engine to me.

but if you have never been into a four stoke before, they are simple. the key part is timeing when you put it all back together. out of time will result in damage to the engine.

the 400ex is simple to time. put the crank on TDC, but the T mark on the flywhee. the line up the two marks on the cam gear even with the head, the third mark should be pointing up. cam lobes should be down, but it really does not matter if they are up or down. it is impossible to get a single cylinder motor 180 out of time so lobes up or down will work but commom practice is to have the lobes face down.

[400exBRAAP]

alright, thanks


i aint to worried about puttin it back together right now, i mean, im keeping it mind as i tear down, like the bolt and stuff like that, but im more worried about how it comes apart, like what has to go where for part x to come off. i pulled the valve cover off, and once i looked inside i was like woah, this is very different. so, im just kinda workin on teardown this second, literally, right now im just taking a break from it actually

[j20accord00]

swinger bolt (pivot bolt)..Get yourself some heat, and a grinder to get the thing out..It took me about a night just to get that thing out..alot of grinding, beating and frustration but it finally came out. Good luck other wise..post some pics as well..everyone loves pics lol

-Evan

[400exBRAAP]

thanks for the advice. but i aint gonna be pullin the whole motor. i already have everything but the jug off. im just gonna rebuild it while it sits in the wheeler. thanks alot though!


Like i said, all i have left is the jug to take off. but that thing seems like it is welded onto the cases. is there any advice i can get to pull that off? i tried a rubber mallet, but she still didnt move. i pulled the 4 bolts from the inside off, then those 2 8 mm bolts off of the side. so what else can i do to get this jug off of there? i dont wanna break any of the fins. thanks for any help, and all the help i have gotten so far.

[400exBRAAP]

anyone? i could really use the help on this one

[440challenger]

its probably stuck on the dowels (rusted)
Triple check you have all the bolts out. They are a pain soemtimes. Work it back and fourth. I know you probably know, but dont stick any pry bars etc between the cylinder and cases. Dont laugh, i saw many people destory there motors doing that trying to "do it there selves"

[F-16Guy]

The first time I had mine apart, I cleaned it really well and before I took it apart I numbered the head of each bolt and it's corresponding hole (1&1, 2&2, etc.) with a permanent Sharpie so that there would be no guess work when it came time to reassemble. It worked like a champ, and the reassembly went much more smoothly not having to try to remember where everything went.

Don't overtorque the rocker cover bolts!! They strip and/or break pretty easily. Get them snug, but don't crank on them.

[400exBRAAP]

ya, good advice. is it safe to spray PB blaster where the gasket is? it would work it back in forth, but theres no movement, it wont budge on bit, so im hoping if i spray PB in there, things might loosen up, but i know PB gets rid of oil, so thats why i ask if its ok to use, if it aint, can i just try some WD 40 or liquid wrench?

[cannibal67]

Is the rocker cover bolts long and about an 8mm? I could'nt get mine started, and looked at the head and there was oil blow out, I checked the bolt and it just pulled out with the threads on it,

now I'm goin to do a tear down myself. I guess the guy that owned it previously could have tourqed it down and stripped it but it was built by pr in ohio where the bike came from.

[400exBRAAP]

well, its all good
i got it off, hit it with the rubber hammer a few good times, and nothing, so i stuck the screw driver under where the fins start, and pryed against the bottom end, NOT BETWEEN THE ACTUALY CYLNER AND CASE. like the inards, i did it right, and she just popped off i then got the piston off, that went easy, cuz i know how to do that really well, ive done many 2-stroke rebuilds. so now its time to order parts. thanks for all the help every one

[F-16Guy]

Make sure the little plunger and spring in the head for the decompression mechanism don't fall out and end up in the bottom end. If you're installing a HotCams cam, just take them out and put them in a safe place now so you don't forget. You really don't want to have to split the case while you're doing a top end.

[400exBRAAP]

ok, i will go check right now, it might have when i turned the head upside down, but i thought it was a washer that fell out, and icouldnt find it. how would it have fallen into the bottom end?

[400exBRAAP]

i did look for it, and i didnt find it, but then i got to thinkin, how could it have fallen into the bottom end? th ejug was still one, and the piston was in there, so the piston would have stopped it, and i would have seen it sittin on the piston i think.


but like i siad, i cant find it, and i wasnt originally planing for a hot cam, but if any body has one, preferably stage 2, cuz what i do is mostly wide open straigh road riding, not much mx type things, let me know, because i may be interested in them.

[LEOGM5150]

i have this cam for sale on ebay right now here are the specs

You are bidding on a WebCam camshaft pulled from a perfectly running 440ex. This item is in great shape, and is ready to bolt on and go. Auction includes: camshaft, bearings, and sprocket. Here are the specs of this camshaft from the website:
Valve Lift: .385/.370
Duration in Degrees: 310
Duration @ .050 in Degrees: 272/270
Grind Number: 463/9i
Special profile designed for racing engines. Must be used with racing springs / shortened guides, high compression piston and exhaust system. Compression release removed. Hardwelded rockers highly recommended!
Check out the website: http://www.webcamshafts.com/pages/honda-atv.html#12

here is the ebay link

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=170180590295&ssPageName=ADME:X:RTQ:MOTORS:1123

[F-16Guy]

The cutout for the timing chain goes directly into the bottom end, but hopefully you're not that good of a shot. If I were you, I'd try to find those parts just for piece of mind.

As far as the cam goes, I would definitely add a cam with the piston. The HotCams stage 2 is very popular, but you might also consider the stage 1. I have that cam and it pulls hard everywhere. If you can find a stage 1 for cheap, don't pass it up just because someone told you that the stage 2 is better. Like the stage 2, the stage 1 has more lift and duration than the stock cam so you will see gains everywhere in the rpm range, not just the bottom and mid.

[400exBRAAP]

LEOGM5150- i saw this cam and was considering it, but isnt that for just big bore's like 440's? wouldnt that be to large for my 416 plans? and would i have to change anything like the valves or the rockers? cuz as far as i know, hot cams you just drop in, but on web cams you have to change some stuff. let me know. thanks


F-16GUY- yes i am watching for any came. i have been kind of not really keeping keen eyes for stage 1's, not becuz people say stage 2 is better, but becuz it seems as if stage 2 is more for what i do, which is wide open high speed riding. but if what you say is true, and stage one isnt just bottom end, then i guess i will be keeping watchfor anyyhing then. thanks for the help so far

[LEOGM5150]

yes the web cam is for big bore or stroker applications and should be used with high performance springs and head mods. also it is recomended to use hard welded rocker arms. i didn't know how far you were going with your build. i bought these cams with every intention of stroking my 440ex and doing all the needed stuff to run it but my friend gave me a set of new stage one hot cams and also offered to buy the 440ex so i had it all together before that cam even got to my house. anyway just thought i would offer it to you. i have the stage one hot cam on my 440 and it really seems to wake up this little machine. i do have head porting and a 12.5 :1 440 kit and it was in boxes when i bought it so i can only compare to other 400ex's i have rode. the stage one hot cam definately improves the top end also on this machine.

[400exBRAAP]

alrighty. thanks for the offer anyway. and thanks for the info on the cam. i guess i can go and order the whole top end kit for 280 bucks off of ebay. but wont it be a pain to be breaking in a piston and rings at the same time as breaking in a cam? becuz weh ndoing a cam, you gotta keep it reving, which is the exact opposite of what one wants to do when seating a new set of rings, right?

[LEOGM5150]

when breaking it in you just want to run it through the rpms smoothly and let it warm up before you go punching it. the most important thing is to not hold it at any particular rpm for to long. you want to keep the throttle position moving throught the rpms. i just wouldn't go hill climbing and drag racing right away mostly just ride around. don't lug it around either. to say you need to break it in for different parts differently is a bit confusing. i mean when you buy any new vehicle all the parts are broken in the same way at the same time just don't try to break it but break it in like you plan on riding it. that's what i have always been told.

[F-16Guy]

Don't worry about the piston during cam break in, it will be fine. During the first startup it is critical to keep the RPMs above about 2000 for the first 20 minutes or so. You don't necessarily need to do it while it's sitting still. When I did mine, I got it fired up and made sure that there were no obvious leaks or problems, and then just rode it around very easily for about a half hour, making sure not to let the revs drop too low. Riding it gives some airflow to keep the engine cool. If you break the cam in without riding it, be sure to put a fan or two in front of the engine so that you have some airflow. Either way should work fine.