Timing chain and new top end build

[4WheelinDemon]

Ok, so i start my quad up and get going for my first real ride on it after i bought it 2 months ago and put the new clutch assembly on 2-3 weeks ago and after getting the ****ty renthal bars welded back together last week right. I start her up and get going. I go about twenty feet to the end of my drive way and it completly dies. Found out its my timing chain snapping :[ (most recent post)...well now i want to know what kind of timing chain is best for my 03 400. I heard that crf 450 timing chains will fit 400's and are better than OEM chains and some heavy duty ones. If that turns out it fits and is better, should i get that or a heavy duty 03 400 one? Or those timing chains on ebay that are listed as D.I.D timing chains? Whats the difference between them?

Now, for the piston...
Should I get a namura piston kit or wiseco kit? Should i bore or what? Whats difference? Namura is cheaper but idk whats the difference. And would +1mm valves give me more power? Are these valves just 1mm longer than OEM or do i adjust the valves 1mm over std setting? Help is greatly appreciated...oh, and im definitly getting a stage 1 or 2 hot cam as well. Which is better? Thanks

[CJM]

Namura is junk.

Wiseco is fine, JE or CP is better but will run you more.

Perfect setup:
10:1 or 11:1 piston (higher compression)
Stage 2 hotcam
Cometic brand gaskets
Buy jets from www.jetsrus.com

Doing that will significantly raise the power and put a grin on your face.

As for replacing the time chain:
CRF450 timing chain from 2002 (same chain as the 400ex but its thicker/stronger
New chain tensioner
New chain guides if worn
You will have to pull the clutch to do this job, its easy but I highly recommendyou buy a clutch holding tool. Rocky mountain atv sells a tusk branded one that works well.

Most important of all: Buy or find (search online) a 400ex service manual.

[4WheelinDemon]

Cosmetic gaskets? Whats the difference between them and oem ones?
And i already took the clutch basket off before and bought the whole entire clutch assembly off a 05 400ex for 99 bucks and it was in almost new condition >:] haha and suprisingly you dont need. Tool for it, i will post a thread one day soon telling everybody how you can remove your basket without a clutch tool. I live in redneck parts so i inherited some of it and thats how i came up of this way that causes zero harm to your assembly.

And as for the chain, i need a 2002 crf450 chain?
And ok, screw namura haha im going with wiseco since my buddy always brags about his in his 2000 tricked out banshee 350 v-twin.

And what about the valves?

[4WheelinDemon]

Just went On ebay and found a je piston kit for about 120. Its standard bore but is 12:1 compression. Would that give the quad a huge kick in power? Or is this a good idea? Or can i bore out the cylinder a bit and drop a je piston in there thats like 40 over with a 12:1 compression? Good or bad idea? Haha

[trxPOWER]

From what i understand going to 12 to 1 is a good kick in the power department. But, you understand that with that kind of compression your going to need to run race gas right?

[CJM]

12:1 is to much for this bike to handle without cooling system upgrades and 110 octane. Remember its air cooled, not liquid cooled.

11:1 is the highest you can go with 93 pump gas. id do a 86mm (406mm) or 87mm (416) bore, plenty of power and you dont take away too much of the cylinder sleeve and cause heat issues.

Leave the valves alone, adding +1 or more will make them hit the piston b/c the higher compression pistons are domed.

Cometic gaskets, not cosmetic are a very good brand of gaskets and seal much better than OEM.

yes CRF450 chain from a 2002 bike. You can use other years but I know 2002 fits.

As for naumra, yea sure they are good. 5 hours on my buddys bigbore banshee and they MELTED. The thing was setup perfect too.

[4WheelinDemon]

Ok, 11:1 it is. But what will give more poer? The 406 or the 416? And dam that sucks for him hahaha im happy i found this out now. And valves will stay the same then, and ill find an 02 crf timer i guess. Now should i get stage 1 or 2 hot cam? Since i have a duel after market exhaust and k&n air filter? And since i will be boring the block as well

[CJM]

higher compression works best with a stage 2 cam. Stage has good low to mid power but has poor topend power.

406 or 416 is very little difference, many just chose 416 b/c its more common. The power isnt the bore-its the compression.

[2001400exrida]

Ok, i'm confused.


How is it that you guys say you can run 93 octane on an 11:1 compression but when you go up to 12:1 you have to run 110?

that makes no sense.

Surely if you can run 93 on 11:1, then you should be able to run 100 octane on the 12:1. not necessarily 110.

[CJM]

Originally posted by 2001400exrida
Ok, i'm confused.


How is it that you guys say you can run 93 octane on an 11:1 compression but when you go up to 12:1 you have to run 110?

that makes no sense.

Surely if you can run 93 on 11:1, then you should be able to run 100 octane on the 12:1. not necessarily 110.

Depends on the jetting, the area the person rides in (air temps, humidity, etc). Some claim they need 100 octane to run 11:1, I run pump 93 with no issues.

Using 110 is just playing it safe. Main problem with 12:1 is it generates alot of heat.

[duroc825]

Use xr400 head gasket to get true compression unless you deck the head

[4WheelinDemon]

Stupid question here lol but uh, if my stock bore is 85mm, what would the cc size be if i go 3mm over? Would it be a 426?

[CJM]

Yes, 3mm (.120") over is 8mm or 426cc.

[2001400exrida]

Originally posted by duroc825
Use xr400 head gasket to get true compression unless you deck the head

i used stock head gasket and i'm getting high compression still.

Originally posted by trxPOWER
From what i understand going to 12 to 1 is a good kick in the power department. But, you understand that with that kind of compression your going to need to run race gas right?



Actually u may not need to run race fuel since the 400ex pistons sit 43 thousandths lower than the actual top of the cylinder at TDC thereby lowering the compression. assuming youre using standard thickness gaskets. I was hoping someone would have tried this by now and would have a solid answer as im considering doing this on my next rebuild and i really dont want to run race gas.

[CJM]

How high the deck itself is in the end does play a role, but need to run higher octane gas is due to predetonation b/c of the heat the compression causes itself.

I highly doubt that extra 43 thousands is gonna matter that much, its still a not watercooled head and will never run as cool as one that is.

Dont chance it is my opinion.