400ex arms on a 250ex howto guide!

[SYKO]

how to put 400ex a arms on your 250ex one way to save you some money:icon_ peace:

things you will need
welder (prefer mig or tig)
cutting torch, plasma, water jet or cnc (i used a cutting torch with a good clean tip)
grinders and cutoff wheels
drill press prefered or if your just awesome with a handheld drill go to it then!
a good measuring tape or ruler
patience and about 4-8 hours of your time

400ex parts needed
upper and lower a arms (durr both sides)
400ex spindles (can be bare spindles)
complete tie rods 400ex

materials needed
3/8x3 flat bar or you can just cut the parts from 3/8 plate
3/8x 3 1/2 grade 8 bolts x8
3/8 nylon spacers 1/4 thick
nuts and washers (I used stainless)
ok here we go.
:macho


now first off the top 400ex arms are to wide at the mounts they need to be cut and rewelded to the width of the 250ex also to keep the correct geometry they need to be welded so the mounts have more toward the inside then the outside (you can plainly see in photos what im talking about)

first remove the seals and bushings from teh 400ex arm mounts, then take your cut off wheel and cut the weld off of the mount

clean everything up so make a good welding surface



now here you need to be kinda precise I dint post the measurements becouse every machine may have a few variables but take the width of the stock 250ex top a arm mounts from the inside of the outer mount full width and thats how wide you want to make your 400ex arms, also take into consideration the bushings stick out another 1/8 inch but dont make yourself to concerned with that Ill show you why later.
I made a jig of some 1/2 flat bar stock and 1x1 box clamped togetther this made sure the a arm mounts stay flat and measured right, alittle masking take helped out


now with the mounts secure and in the correct measurement tack the a arms on top (this is no problem and they stay lever unless you got some bent arms) also give them a bit of space between the arms and the mount to take the palce of the weld you previously cut off and give enough room for a good penatrating weld

now easy rotate the mounts and tack the bottom

[SYKO]

remove and finish weld them up


of course some may need to be grinded off the ends to make everyhting smooth and flat and within the measurements




now onto the top arm mounts

the top mounts on the machine are to far inboard on the 250ex compared to the 400ex so a widening plate needs to be made, once again I dont have the measurements on hand but I will get them for this.
it is rougly 2 inches wider on both sides then the 250ex
I made a cardboard template wich I cut and transferd to the 3/8 metal I had on hand
I used a cutting torch and then cleaned them up with a grinder
also notice one mount is differnt then the rest its cut out to fit around the stock brake line mount the other 3 are all the same, you could in fact make all 4 the same and just gut the brake line mount off and weld it to the mount or do something differnt its up to you
(also note diamond J top widening mounts may work in the place of making your own mounts, but I havnt confrimed this or know their measurments, could take a shot in the dark and not have to do much work but dunno.)


you may not be able to notice in the pics but where the mounts go under and around the stock frame they need to be cut for the stock frame weld clearence. 45 degree angle worked fine for this.

also to drill all the mounting holes I used a drill press with a 3/8 bit, I tacked every mount together and drilled through them all to make sure they all have even straight holes. The two inside holes match the stock 250ex arms and are used to bolt the mounts and the outside of course are 400ex arm bolt holes

[SYKO]

now you can mock up everything to make sure you havnt royaly screwed up your or your kids ride


everything is loose in these photos



now if everything fits and looks like it will work take it all apart and at least spray paint I prefer high end paint no rattle can here



ok now when I started putting the front end back together I found out a few things
first, you have to continue to use the inside 250ex rod end as they are a larger mount bolt then the 400ex rod end
also the 250ex spindle wont work with the 400ex arms unless you get some spacers and washers as the ball joint on the 400ex is quite a bit larger then the 250ex ball joint. Thankfully I had a extra set of 400ex spindles laying around to use, the hubs and brakes off the 250ex will bolt on with no problem.



now you can see here how the top arms mount and where the nylon spacers need to be put, later I may get some aluminum spacers


up close


notice the stearing is realy tight on the 250ex it may be the 250ex stock stem difference then the 400ex or the roll design stem on this 250ex dunno but it turns way tighter then a stock 400ex



now sit back and look at your great feat of weekend enginearing!!
also note the stock 400ex bottom arms bolt right on with no modifications at the exact same measurement as a 400ex



this only adds about 1 3/4 inches per side but its suprisenly feels wider then that, later I may try 450R arms as they will add another inch to each side.
all in all I got about $80 tied up in this (a arms- tie rods- hardware) you may spend less you may spend more but whatever it is its a cheaper allternative then aftermarket arms.

[SYKO]

I found my template this was scanned into my computer if you copy and past it and expand it to fit regular printer paper it will be the correct size to copy off of



if you just print off the picture it wont be the correct measurements

basically the new outside holes are exactly 2 1/4 inches further out then the stock 250ex top mount holes so just blow the tremplate up and print and measure to double check and you should be good.

[joeylowthers450R]

awesome mod and nice detailed writeup, i have never compared side by side(250/400) but from the looks of your pics, the 250 shocks are alot shorter then the 400 shocks. so my thoughts were, maybe you could fab another set of plates like your upper a-arm mounts to bolt to your upper shock mounts and mount 400 shocks to gain more travel(and set your ride height where you want)

last thing i can add to this is 450 arms are diff then the 400 arms, so be ready for a little more fab work on the arms mounting points

[SYKO]

glad you chimmed in about the 450's I got another set of arms (extended 250R) they are getting sent off to get modded since I dont have any way to weld chromoly here so the new arms will be +4 over the stock 250ex. And I got a set of 450R shocks that im going to send off to get revailved and resprung with tripple rate springs for it as well and I will be making a add on upper shock mount relocator and Ill make a write up on it as well. Right now the 250 shocks work just fine but I want the 450's on there by the time she starts racing.