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Thread: 400EX Step by step motor build

  1. #1
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    Sep 2010
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    400EX Step by step motor build

    Ok yall, heres the motor build I was talking about last week. My first writeup I have ever done so take it easy on me lol. Hope this helps someone.

  2. #2
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    Sep 2010
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    Here we go I started the build idea once I installed the crank. So thats where I have to start...
    Install New crank bearings and crank/balancer making sure to align timing mars on crank gear and balancer.


    Once the crank and balancer are installed you can start installing your transmission parts. First things first put the countershaft and mainshaft gear sets together while holding them in your hand and insert them into the case at the same time. making sure that your thrust washers are on the top and bottom side of the mainshaft and on the bottom side of the countershaft.


    After you get them in place put your shift forks in their correct place, they are marker which is center C right R and left L. It is easiest to get them in place BUT leave the locator shaft out of the holes untill the drum and linkage is in.

  3. #3
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    Sep 2010
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    You can now put your shift linkage and drum in place making sure that the return spring pin is screwed into your case and the steel legs on the linkage go around it (one on each side) You can now also put the nipples from the shift forks into the drum. I usually put them in the most counterclockwise position on the drum as this is first gear. once their in the drum go ahead and put the shaft into them securing them in place


    That is all that is in the bottom end of a big bad 4 stroke, not much to it, now its time to put the cases together...
    I personally put a THIN coat of ultra copper on the aluminum surface of the cases because I dont trust a paper gasket and I do not want to take the chance of having a leak when it all together. I have never had a leak when using this stuff in combo with a standard paper gasket.


    When putting the cases together make sure the 2 dowel pins go in and dont rip the gasket instead.


    Once you have the cases set together they usually go together really easy but if they dont set by themselves just give it a little tap with a rubber mallet or dead blow hammer. You can now put in the case bolts. I believe there is like 13 (not 100% sure on the number) on the left and there is 2 on the right side. Tighten the bolts in 2 or 3 steps and in a criss cross pattern

  4. #4
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    Next install the oil pump using a new steel gasket underneath and a new 3 hole rubber o-ring gasket on top.



    Now install the Timing chain sprocket, after you install the timing chain sprocket PUT YOUR TIMING CHAIN ON! (i forgot in the pic lol) once that sprocket and timing chain is on then put the main sprocket on and then the oil pump drive sprocket. All 3 of these will only go on one way with the flat tooth of the sprocket on the wide tooth of the crank shaft. Then you can put the oil pump driven sprocket on and put the washer and bolt on and bolt it all together. It may be easier to wait for the clutch and flywheel and cylinder to be on to tighten it all the way so it will have some resistance.



    After that you should put the shifter star and linkage on. First put the spring over the boss like so...


    With the spring on you can now put on the stopper arm and hold it back (it takes some force now that the springs on) and put the shift star on being sure to put the dowel pin into the star/top of the shift drum.


    After that go ahead and install your timing chain guide


  5. #5
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    With the shift star and stopper on you can now put the clutch on. First make sure you put the outer guide onto the shaft...


    Then install the outer basket and thrust washer...



    then put the inner basket inside of the outer basket...



    You can now install your plates. It starts with a fiber then alternates fiber steel fiber steel...the last plate will be a fiber and it goes in the shallower slots of the outer basket like this...


  6. #6
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    After your plates are in Put the thrust washer on the shaft and then the lock washer with the OUTSIDE make facing well...outside.... and then put your nut on and tighten it and use a punch to lock it in place in the little hollow spot of the shaft.



    After this put the pressure plate on being sure to put the lifter in it first (It really only fits in one way) and then you can put your clutch springs on. For the clutch springs there is no torque value they give so just bottom them out and then tighten JUST A HARE PAST THAT, NOT MUCH AT ALL OR YOU WILL BREAK THEM!! By just a hare i mean like 7 ft pounds max! after that your done with the clutch



    As for the flywheel side im sorry but I lost most the pics (no idea how) but I do have one important one. MAKE SURE before the starter gear and flywheel go on, which should have come off as 1 piece anyway, make sure your woodruff key is in place and put the thick spacer and bearing on the shaft and then slide the starter gear.flywheel on and bolt it in place.


  7. #7
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    After the flywheel is on I usually put the piston and cylinder on. Now I didnt get any really good pics of this as i was alone doing it and it kind of takes 2 hands and i had no one to take pics but the easiest way I find is to just slide the piston on, put the oiled pin threw and use a pic set to put the circlips in place. I did not do a write up on putting the rings on the piston as they were already on my piston sorry. Once the piston is on I slide the cylinder over top the piston letting it slightly rest on the top ring, I then push the rings together with my fingers one at a time and let the weight of the cylinder do the work. BEFORE you do this though make sure you put a new base gasket on and a new o-ring on the bottom of the cylinder



    Once that is on or in the process of putting it on you can fish your timing chain threw and just hold it in place with something to keep it from falling back down. Also a good time to install your other timing chain guide.



    Once thats done you can go ahead and bolt the head on, again fishing your timing chain threw.


  8. #8
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    After the head goes on you should install your flywheel cover and gasket, first Installing the starter gear and shaft into its spot.




    After the cover is on set the motor to TDC by turning the motor counterclockwise with a 17mm socket on the flywheel bolt and aligning the T mark in the viewing hole. (At this point there is no compression stroke sense the cam is not in so just align the T and your good)
    Once your at TDC take your cam sprocket (sprocket only) and put it "into" the timing chain so that the 2 lines are even with the deck of the head then slide your cam/bearings thew and bolt the sprocket to the cam. Once the cam is in make sure your 2 bearing setting pins are in place to.



    your timing is now set. you can now put on your valve cover and bolt it into place, put on your tensioner and check your valve clearance. I did not get any pics of my checking the valve clearance but its very easy. Just put the motor back at TDC this time on the compression stroke and take the timing caps off. The valve clearance per the honda manual is .10 intake and .12 exhaust. You just loosen the lock nut, unscrew the little screw a bit and put the appropriate feeler gauge between the screw and sub rocker and tighten the little screw till there is a little drag on the feeler gauge then tighten the lock nut and double check with the feeler gauge, if there is a little drag on it your done, move on to the next one. When all of them are done you should rotate the motor a couple revolutions and then put it back at TDC and re-check them just to be sure.

  9. #9
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    Now you can work on the starter. Put the other starter gear and shaft in place like so, with the thick washer on the outside, the push your starter threw and bolt it in place and put the cover on, now thats done...



    After that you can go ahead and put the clutch cover on. Only thing here is to turn the clutch shaft A LITTLE counterclockwise so that when you put the cover on it grabs the lifter and engages into the rod.
    Well, thats pretty much all there is to it. Not to bad right?! now go out there and put your own motors together, its really not that hard!

    FINISHED...

  10. #10
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    Sep 2010
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    OK GUYS IM DONE. lol. I have never done a write up like this before so take it easy on me. im sure I forgot to say something or left out something you consider important so feel free to add whatever you want. I just wanted to show that its not to hard to build a motor and hopefully someone will learn something from this and it will help someone out. Also, I did this VERY fast so im sure there is lots of typos and spelling errors, I will try and go threw it and fix them at a later point lol.

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