Help on rebuild

[Westro]

My father's 400ex is smoking, so I'm pulling apart the top end.

Any tricks I should be looking at? If I pull the multiple 8mm bolts will the head come off the cylinder or is there a timing chain that is going to give me trouble.

Any help would be great

[Westro]

I assume that I have to pull the clutch side cover to remove the timing chain? Also how is timing then reset on the valves.

Thanks

ok.. ill lay this out for you.. nice and simple.. Unfortunatly i dont have pics, thats just because my ahnds were too greasy to grab the camera..

First off pull the plastics.. you obviously know how to remove the rear fenders, the front fenders have 2 10 mm bolts on each side right over the front wheels.. Then you will have 2 10mm bolts holding the bottom of the black panels on.. There may be some of those pushpins holding the tank cover on.. to remove that, remove the pushpins, remove gas cap, then remove the tank cover, put the gascap back on..

Now you have the plastic pulled forward, reach in there and disconnect the electrical stuff, its not that hard, but it is tricky with the latches of 2 of the connectors..

Now the plastic is out of the way.. turn your bars to one side to see the 10mm bolt that holds the tank on.. pull that, and then do the same for the other side. On the side of the tank, theres 2 rubber straps that have to come off also.. Down on the carb, remove the fuel line from the carb, before you do that, MAKE SURE THE FUEL IS OFF! Now you can pull the tank and sit it to the side. Now remove the heat shield via the 2 10mm bolts on the sides of it, set that aside.. Im not sure if you have the snorkel on the bike, but that will need to be removed also, i dont have one on mine so i cant really tell you how to take that off..

Now what you have is the top of the motor.. You need to remove the 10mm and 6mm flywheel and timingwindow covers.. thats on the side of the shifter.. you will see them right in the case.. ones dead center, the other one is about 10 oclock on the round of the cover.

Now some people may disagree with me on this, but ive done this many times, and have yet to run into a problem.. so i believe its safe.. Remove the upper engine mount via the 14mm nut and bolt, and slide that out.. Now take and remove the 8mm bolts from the rockerbox and the one 12mm bolt in the middle of the rockerbox.. Remove the rocker box, be sure to not mess up the metal gasket, you will be reusing that.. Some oil will drip out but thats normal.. Now it doesnt matter where the motor is, in its revolution, Rotate the engine till you can see the cam sprocket bolts.. they are 6mm allens.. Remove them, and set them aside..

Now here is where it gets to be a PITA.. Remove the cam chain tensioner.. you dont have to worry about pulling the tensioner back on removal, but YOU MUST DO IT ON INSTALLATION! Take the tensioner out.. then turn the motor till you can see the 6mm allen head bolts that hold the cam sprocket on.. set those bolts aside.. Take the sprocket and move it off of the cam, to where it stays up but leaves alot of slack.. Remove the chain from the sprocket and wrap a peice of wire around it and tie it up to the frame.. That is a MUST.. or you will be hating life..

With the cam chain tied up, carefully lift the cam outta the head, and becareful NOT TO DROP ANYTHING INTO THE MOTOR.. take note of whiceh way the bearings are facing, incase they come off.. set the cam and the sprocket off to the side.. Now you can remove the plug, but i usually leave it in, to keep crud outta the engine until the head is pulled.. the cleaner the better..

Now take the nuts off the head studs.. i believe there are 4 of them, and they are 14mm (im pretty sure on that size).. Mine were acorn nuts, but ive heard others are just standard nuts.. So reguardless, they need to come off.. now once you have the nuts off, You need to rid of the exhuast.. they are 12mm bolts (or maybe 10mm) remove them, if they are rusty soak them in some penetrating oil before you try to turn them.. once they are off, remove the muffler, and then the head pipe.. now listen up.. the headpipe comes out ONE WAY and goes in ONE WAY.. take note of the clutch cable, where it is in realtion to the pipes.. its easy to put back on and be way outta line with the clutch cable..

Now with the exhuast out of the way, remove the airbox boot, and the carb, i took mine and just hung it over the handle bars, it was fine.. now you can pull the head.. it should just come right off with no trouble, but if it does DO NOT USE A SCREWDRIVER TO PRY IT APART, instead tap it with a rubber mallet.. the head has to come STRAIGHT off of the studs, so keep that in mind.. It helps to have a extra set of hands for the timing chain, so use long enough of a wire so that when you lift the head up, you can hold the timing chain up, and tension kept on it, so you can tie it back off..

Now you have the head off.. take a look at all the stuff, the valves, the piston relifs.. make sure the valves havent smacked the piston.. Just to make sure yanno.. Now you can pull the jug.. pull the 4 14 or 12mm bolts out of the head and sit them aside.. if there is ANY discoloration of the bolts, buy new.. or of they are even slightly bent..

Once they are pulled, do the same thing that you did with the head and timing chain deal.. have somone hold it, slide the jug up, off the piston, and sit that aside..

Now you have the top end of the motor off.. Take a look at the jug, is the factory crosshatching there? if its not, then just hone it out a little and be done with it.. but.. what i would reccommend is to get it bored and then get a new piston.. eaither or, both will be fine.. just boring it gives it a brand new surface to seat on..

If you hone it.. use wd-40 and go in and out. with the hone.. dont get nuts with it, or youll remove too much.. If your not going to do the bore, then remove the rings, and go grab a new set of rings..

Now when you install the rings, they go in a certain configuration.. from the top ring, to the bottom oil ring.. The rings should have instructions on them, if they dont, ill post up how to do it..

Put the new rings on.. and get a 4 inch hose clamp and put around the piston and the rings.. you dont have to have it tight.. just get it around the piston, then back it off a half a turn.. slide the jug over the piston rings and let it fall into the cylinder..

Then just reverse all the steps to reassemble..

Torque is 35 ft lbs on the cylinder bolts, and 33 on the headnuts (im pretty sure.. it isnt too far off if its not correct and im sure somone will pop in on this)

When you get it back together, ill tell you how to retime it.

Jesse

[walt miller]

you do not have to take the timing chain off. just remove cam chain tenctioner and cam sprocket. do your self a favor and buy a manual

[Westro]

I know my way around the Honda's the 400 is very close to my R. The 4 stroke aspect is what is throwing me.

I'm getting a manual, but the instructions are great.

So, is it going to be a ring or a valve that is passing the oil? Is this common? My father is 50 years old and doesn't beat on it, and it started burning oil. It is a stock 1999.

[walt miller]

it could be a valve stem guide or a blowen head gasket

[Westro]

ooooohhhhh head gasket would make alot of sense

[ReconRider25]

when does it smoke? if its when you first start it up it could just be a bad valve seal.....

[Westro]

It smokes all the time. Even after it is warmed up and of course under hard throttle.

[crazyatvn]

I would say mostly rings but I would replace valve guide seal while you have it apart. I had an R too the motors are nothing alike I would definitely get a manual.

[Westro]

Chassis wise…the R and 400

[josiah400ex]

thanx, that's alot for good info......

good link, This website is very helpful.....

[DieselBoy]

I'm willing to bet your bore has gone sour....

[wheeltrax]

Originally posted by DieselBoy
I'm willing to bet your bore has gone sour....

how do you figure lol. usually the bore doesnt go bad. the rings will go bad before the bore