06 400ex My first build!!

[Jesse400ex]

Well I have been doing a lot of research and reading up on the different builds for the 400ex. I picked up an 06 400ex that’s pretty much stock except for having a jet kit and a knock of brand k&n filter. It dose however have a great set of moose racing nerfbars with the heel guard, and moose and monster graphics. I have a bout 1900 in it, I thought it was a good deal for an 06.

I have decided to go with a .040 over hi compression 11:1 piston, I think that would be a 406cc, stage 2 hot cam and DID cam chain, hmf slip on pipe, dyno jet kit, and I ordered this used air filter and aluminum adapter plate that dose away with your stock air box, have you guys heard of anything like that?

I was also thinking about doing a port and polish and grinding out the welds in my header? Would I see any gains or would it be a waste of time. This will be my first rebuild on a four stroke engine, so just looking for advice or pointers, maybe something I have missed and maybe a starting point on what jet size to use. My buddy has an 01 660 raptor, I’m hoping to be able to hang a little better with him, but will see.:D

[trailrider894]

I think if you are gonna bore it over... go to atleast a 416 or 426. The gains from a 406 are going to be very very small... and keep in mind that when you make the bore bigger it makes more heat, so you gotta keep the engine cool. So you can get an oversized oil tank or oversized cooler. Or you can install a 4" spal fan on the oil cooler.

[Jesse400ex]

I already have the piston, but the upping the comp to 11:1, that’s were I'm going to see my increase.

[bkelley]

Originally posted by Jesse400ex
I already have the piston, but the upping the comp to 11:1, that’s were I'm going to see my increase. Yeah, even a stock bore 11:1 piston along with a cam will produce some nice gains.

I would stay away from DynoJet if possible. Genuine Keihin jets are much easier to deal with. As for the no airbox setup, be careful. In ideal conditions it's great, but you'll go through filters fast and you have to be careful around water. I've been running without an airbox for a little bit now and I'm already planning on building a custom aluminum box. A P&P job will help open up the top end and grinding the header welds will help the engine breathe a little better.

[beags86]

kelley- think you could post a pic of the air filter set up with no box, i have been thinking about doing that.

[bkelley]

http://img694.imageshack.us/img694/3529/dscf1071k.jpg

[Jesse400ex]

I dropped my jug and head off at the machine shop today. I took a dremel tool to the welds in the header, I couldn’t believe how much weld was actually in there. I cant wait till shes back to gather. If I’m missing anything feel free to let me know. I will definitely be careful with the airbox mod, the aluminum part is on eBay if anyone wants to look at it. Dose anyone think I will hang with a 660 raptor?

[TRXRacer1]

Ditch the DID cam chain and go with a crf. P&P will be a waste on this build, the stock head flow plenty. Good choice on the piston but like said earlier the DJ kit is a joke. If you want an adjustable needle I have a couple PM me.

[Jesse400ex]

Kelly what is this Sparks +6° Key in your sig?

[TRXRacer1]

Originally posted by Jesse400ex
Kelly what is this Sparks +6° Key in your sig? Nothing you want with an 11:1 and a stg 2 but I have a +3 that would work.

[Jesse400ex]

What is it?

[TRXRacer1]

Originally posted by Jesse400ex
What is it? Timing advance. You replace the stock flywheel key with a degreed key. Changes ignition timing and makes more power. Makes more heat too that's why with your build I would not recommend it. +6 is best suited for stock machines.

[Jesse400ex]

were do I get one and will it help on my setup?

[TRXRacer1]

Originally posted by Jesse400ex
were do I get one and will it help on my setup? You get it from me. I have a brand new +3 never used. I ended up going to radical on my build and never used it. It would be perfect for you. $20 for the key and needle + shipping.

[bkelley]

Originally posted by TRXRacer1
You get it from me. I have a brand new +3 never used. I ended up going to radical on my build and never used it. It would be perfect for you. $20 for the key and needle + shipping. That's a good deal. I would jump on it if I were you, Jesse. Make sure you get the fly wheel puller, too.

[Jesse400ex]

Well that’s one thing I haven’t researched. What kind of improvements will I see and how difficult is it to remove the flywheel, correct me if I’m wrong the flywheel is under the left side cove right? Changing the timing you said wont cause me engine to over heat?

[bkelley]

It increases throttle response and adds to the low end. It's a fairly simple install, I did mine in like thirty minutes. With the +3° you temps will be fine.

Here is an install guide.

http://www.atvriders.com/articles/timingkey400ex.html

[beags86]

Originally posted by bkelley
http://img694.imageshack.us/img694/3529/dscf1071k.jpg


sorry jesse, not trying to hi-jack the thread.
-kelley that looks homemade, and alot like i was thinking about doing. is it homemade? or did you buy or build that tube piece in the middle?(with the mount on it, not the black flex tubing)

[Jesse400ex]

I called the machine shop today to see if my jug was ready, and they told me when they were boring it the sleeve came loose and spun around in the jug. Has any one ever heard of this? Now there telling me I might need a new sleeve or a whole new jug. It sounds kinda strange, I mean its an 06, why would that happen.

[416racer]

The same thing happened to me when I had my bore done. They were able to reset the sleave on mine and it's been fine for a year now. The only thing I noticed after it was all done was they bored to a 426 not a 416 like we had planned.I don't know if they had to bore it again after it came loose or what,but I didnt realize it was a 426 till I started looking through the boxes the parts came in and seen it was the bigger piston (88mm I think) anyway it's been fine since.

[Jesse400ex]

They haven’t told me that I need a new piston yet, I just brought them my piston and jug, I just didn’t know if it was something the machine shop did and just didn’t want to take responsibility for it. If I do need to go over than I guess I have a piston for sale.

[TRXRacer1]

When a sleeve spins the tool can gouge and depending where they were (depth wise) in the boring process they may have to go to the next size up in order to clean it up. Hopefully you're all good.

[Jesse400ex]

I have a new problem now, when I changed the timing chain and had the clutch basket off, well when I put everything back to gather I had to adjust my clutch about 3/8s? What would cause my clutch cable to become loose when I had no problems with it before?

[Jesse400ex]

anyone?

[TRXRacer1]

Still thinking. Is it working correctly?:confused:

[400exrider1990]

Originally posted by TRXRacer1
You get it from me. I have a brand new +3 never used. I ended up going to radical on my build and never used it. It would be perfect for you. $20 for the key and needle + shipping.

just random ? what degree key could i use to gain more power out of my 440ex... if a 3 degree would be god i would be interested in buying..



440ex 12:1 commpression
gt thunder heavy duty studs- a must!
white brothers slip on
k&n air filter w/o air box top
edelbrock carb-no clue what jets are in it
aftermarket cdi box
aftermarket rectifier
amr monster coil
stage 2 hot cams
heavy duty timing chain
hot rods heavy duty crank
hinson clutches
ported and polished head

[bkelley]

If you want to advance the timing at all with a high compression piston you have to make sure you are always feeding it 100+ octane to avoid causing detonation. Wheelie's +3 keys match up well with high compression pistons and high octane fuel.