What is a good mx bike build?

[trailrider894]

Hey guys, i am rebuilding my 400ex this winter and i am wondering what you guys would do to make a budget MX 400ex? I am also wondering about skid plates? and what Sprocket sizes i should use with a 20 inch tire. or should i get 18's??

[slightlybent47]

You need 18”s on the rear and 20”s on the front, then you need a +4 axel and +2 a arms, then you need 450r shocks in front and rework the rear shock or spring for a elka rear and 450r front shocks. You will need nerfs and a kill switch if you’re going to race but I recommend them anyway even if you don’t race.
That will get you up and running and then you can do the motor later unless you want to do it at the same time.
You can get all these parts used and it will save a lot of money.

The motor will need work to, so you’ll need to, bore it, port it, cam it, pipe it, carb it, valve it.

[mineralgrey01gt]

i got my full front end for my old 400ex off of ebay for $500 shipped, it was works shocks with rezzies and full flight +2 arms and put a fresh 450r rear shock on (not much of a difference over the stocker but my stocker was shot) and ran riken grooved radials (came up to a 20" tire) on the fronts and grooved turf tamers (18x9.5x8) on the rear. Here is a pic of it before I got rid of it:

during my enging build:
http://i673.photobucket.com/albums/vv91/lilzilla2008/photo5.jpg

after it was all done:
http://i673.photobucket.com/albums/vv91/lilzilla2008/IMG_0402.jpg

http://i673.photobucket.com/albums/vv91/lilzilla2008/IMG_0403.jpg

http://i673.photobucket.com/albums/vv91/lilzilla2008/IMG_0401.jpg

also heres a shot of my 250r that was mx ready also, had stock front end up +4 rear and 18" and 19" tires:

http://i673.photobucket.com/albums/vv91/lilzilla2008/digicampics191.jpg

http://i673.photobucket.com/albums/vv91/lilzilla2008/digicampics194.jpg

http://i673.photobucket.com/albums/vv91/lilzilla2008/digicampics195.jpg

http://i673.photobucket.com/albums/vv91/lilzilla2008/digicampics196.jpg


yes im pic whoring a little bit lol

[trailrider894]

Originally posted by slightlybent47
rework the rear shock or spring for a elka rear and 450r front shocks. WIll you explain this a little bit more?

[FL-R]

Just get some +2 or +3 A-arms. +4 axle. And 450r shocks will wrok, but if you can spring for a nice used set of PEPs or Elkas, Std travel works good. But if ur seriouse and have the coin, go LT. I have a decent set of +2 arms, (chrome is in ok cond) and some triple rate comp adjust- rezi PEPs for sale, they need to be rebuilt but its a good start. 400$. Then some nerfs and a kill switch. You can run 20s for now but will be alot better with 18s. And im runnin the stock rear shock. It does OK. Heres a pic of my MX 426.
http://i21.photobucket.com/albums/b262/southernkrawlers/4aec65d0.jpg
http://i21.photobucket.com/albums/b262/southernkrawlers/ebmx5.jpg

[slightlybent47]

Originally posted by trailrider894
WIll you explain this a little bit more?

The rear shock is actually not that bad of a shock like the front ones are and can be rebuilt to make it better and work for your weight.
Most shock guys can do this for you and should run around 60 bucks. Or find a good used elka and have it serviced like I did, I must say that the elka made the biggest deference in the corners more so then the jumps in my case over the stock shock. When I put the elka on I immediately felt it stay flat in the corners and it had less body roll when cornering. I bought a slightly used elka for $400.00 and paid $60.00 to rebuild it and it has worked out great for me, a new elka like the one I have is $900.00 + tax.

I also have a set of 450 shocks on the front with my +2 a arms and it works real good as well. I bought the 450 shocks used for $100.00 and they only had one ride on them so I just put them on in stock form till I wear them out and have them re built as well. Since they were new I figure I’d wear them out first before I rebuild them and make them better.

Hope that clears it up some for you.

[trailrider894]

What about skid plates??? I have heard mixed opinions about them? should i run them or not?

[slightlybent47]

No there not needed for mx riding, put the money on something else. When mx riding you want to be light as possible and besides there are no rocks or logs to ride over so there useless for mx. But if you trail ride with the same bike and depending on where you ride you may want them.

[trailrider894]

What other things can i do that won't cost me too much money that i can do to make my quad stronger? Like frame modifications and removing of things... etc... What about making a custom airbox to relocate the battery? will that help at all with weight distribution?

[slightlybent47]

Some people gusset the frame to make it stronger in key areas but you got to be hitting some big jumps to warrant that mod. Changing the air and battery box to an aluminum one looks real nice but it wont make it go faster or ride better.
One thing that helps is getting a AVS easy pull clutch leaver, it wont make it go faster per say but it will let you shift easier and better and that may help you a little bit, I like mine.

There’s not much you can remove that you don’t need to make it lighter, you pretty much need everything that’s on there except for the tool kit.lol
I don’t see a arms in your sig, do you still have the stockers on there now? That would be a good mod for you. If you can find some used a arms in a +2 or +2 long travel would be even better.

[trailrider894]

I have +2's in the mail right now. What wheels should i use?

[rpfeifer11]

Douglas wheels. Yellow label rolled edge fronts 3-2 offset depending if you got +2 or +3. Yellow label beadlock rears. You should get a full frame skid plate. People that dont use them are the ones that flat land on a rock and put it through their bottom end or put a massive kink in their frame. I never run without my skid plate. dont get a arm or swingarm skid plates though.

[slightlybent47]

I like the ITP Baja T-9 rims, there cheap and they hold up.

[trailrider894]

Well i have a chance to get a DWT sponsorship.... I had one when i raced a million years ago...

[slightlybent47]

if you can get a sponsor that would be great every little bit helps. I’ve only used the ITP’s so I can’t compare them. Here’s my ride. http://i52.tinypic.com/117crv7.jpg

[trailrider894]

I have about a half a dozen sponsors... lol

[FL-R]

3-2 have way to much bump steer.4-1 handle better and are easier on balljoints.

[IMSROLL450R]

Originally posted by FL-R
3-2 have way to much bump steer.4-1 handle better and are easier on balljoints.

I'll second that. Your forearms will thank you for 4:1s......

[trailrider894]

what about 3:2 with a steering dampener?

[FL-R]

Might work, but just double the money, How bout best of both worlds, 4:1 and a steering dampner.

[rpfeifer11]

I have used 3-2s my entire racing career and never had a problem with bump steer at all.

250R imo would be besty to build. who else than me have twist on their 440 ?

[trailrider894]

Yeah... with +2's how wide is your quad with 3:2's? And do you have a picture of how wide it is?

[rpfeifer11]

He never said exactly which a arms he was going with but he said he was on a budget so most budget people that want a good front end go with the +2s and stock 450r rebuilds. You never really see too many +3 standard travel a arms. I have houser +2.25 a arms on my 450r with 3-2 wheels and I am at 49.5 inches. I believe the 400ex is narrower than the 450r in stock form so even if he got +3s couldnt he still run 3-2 wheels and be under 50 inches? I am just trying to help since he asked questions that I know how to answer. Here is a pic of my front end by the way.

<a href="http://s268.photobucket.com/albums/jj16/S1L3N7xF0F1DDY/450r/?action=view&current=022.jpg" target="_blank"><img src="http://i268.photobucket.com/albums/jj16/S1L3N7xF0F1DDY/450r/022.jpg" border="0" alt="Photobucket"></a>

[FL-R]

Give the 4:1 a shot if your buddie has a set. They do help. I use to run +2s and 3:2 rims, then to +3 and 3:2, now im at +3 and 4:1 and love it, And with no stabilizer on Both my 426ex and 250R

[trailrider894]

Well I Got +2 A-arms. I would like to be right at or in the area of 50 inches. I don't want anything to crazy... so i am just gonna go with 3:2's for now, and find a dampener if i feel it is needed. What dampeners are you guys using? what is the best style or kind that you know? ( this thread is gonna be LOADED with information!! Good reference point for other people, i am trying to ask all the questions i can. )

[rpfeifer11]

I was running a gibson stick stabelizer 7 way adjustable last season and got the precision in the picture last winter for this year and had it on for 1 race and ended up buying another new gibson. I know the precision is about 3 times the price but the gibson feels so much better. For $150 you can't beat it and it helps out greatly. You are going to need a stabelizer if you are riding on a track using 4:1 or 3:2 offset wheels. Handling is the best modification you could ever do to a quad but pros would not run 3:2 offset wheels if they killed you. I have never had a problem and either will you.

[trailrider894]

why would pro's never run them?

[rpfeifer11]

I don't think you read my post right but in other words. Some pros run 3:2 offset wheels depending on the front end they have and they would not run them if they gave you rediculous bump steer. Sorry if I made it complicated.

[trailrider894]

Hey, man... no worries about it. I get it now. lol You guys have been saving me a ton of work!! It means the world to me, to know that there are guys out there willing to help out a poor soul like me, and answer my silly questions.

[trailrider894]

How much Camber should i run? i am not really sure how to phrase that? *where should i have it adjusted too? I hope you guys know what i mean?

[rpfeifer11]

For camber I believe what I did was got a square and put it against the tire and then made the top of my wheel in about .25 of a inch. If you set it at that and it looks like it's leaning too much than make it like .2 in or so. The biggest part is getting both of them the same. I don't know how I did it but I adjusted my whole front end in about 10 minutes and I refuse to touch it becuase I will never get it this good again.