400ex Head

[FoxMxRiders]

I don't know how to say it in english but the traduction is : to plane the head.In french this is " planer la tete " that is to take off a sleep on the head that way the combustion chamber will be a little smaller.Then the compression ratio is bigger.

I want to know how much I will need to take off to have a good compresion ratio without running on racing gaz,I run on 91 octane and which head gasket I will be better to run.

I have the stock ratio : 9.1:1

Thanks

[GPracer2500]

Why not use a higher compression piston instead? Seems easier. [shrug]

[bh2285]

This is a 440 ex motor it has a j&e 12:1 piston,ported and polished head,white bros valve springs,xr 400cam,the head and cylinder have been decked .025,the head studs are9/16 in diameter instead of 10mm and they are 1in. longer than stock. Carb has the choke removed and is tuned to this motor.


Here is my setup Mine was decked .025

[FoxMxRiders]

decked ... here the way you say it :D

I don't want to use a high compression piston because I have the stock one (2001) with 120psi of compression and it don't take oil.He run very good also.

Here the mods I have :

Uni Filter
Open box
Yosh slip-on
Dyno jet kit

Here the futur mods :

advanced timing +6
thicker head gasket
decked the head to raise the compression ratio.

Do you think that's a good idea??I dont want to run on racing fuel ... do you think I can have trouble running at 91 octane? and with the headstuds?!?

When you say .025 thats is in mm then 0.001" ??

[bh2285]

Yes decked is the proper lingo but I knew what you ment!! I think you sould just go with a new pistion before you go into all the decking and such. I have to run race gas in mine... as far as the studs mine where pulling out after I decked it so I had my buddy put bigger ones in. Solved it. Runs good besides me sucking at setting the lash.

[FoxMxRiders]

Thanks for the info

Bad or good do you think??

[troutman561]

Go with a higher comp piston, and as long as you dont go over 11:1 compression on the piston you can still run 91 octane.

[FoxMxRiders]

Yeah I know that but don't want to but a lot of money into it :rolleyes:

a 416 Je 10.8:1 is around $145 can
Hotcam stage 2 is $180can
CRF450 timing chain : $53can (maybe need one!)
Cometic Gasket is $63can

Then 441$can because I can do the job myself.

Sound like a little much for me...im low in cash !! :(

I can have the decked job for fews bucks then not to much!!

Then I do it or not :confused:

[GPracer2500]

I thought decking the head of an OHC four stroke would throw the cam timing off just a little. Maybe not enough to matter though.

I guess you could always use a slotted cam sprocket and set the cam timing manually if it needed to be perfect.

[GPracer2500]

Not sure why your throwing the cam and timing chain into your cost figures. You don't have to change cams if you install a new piston. And the timing chain--if yours needs replacing then it needs replacing whether you do anything to your motor or not.

[FoxMxRiders]

yeah I know about the timing chain.

Because If a put a brand new piston in it,that will be helpfull to use a cam to put out more power!!

I think about rebuild it :confused: I will check that

Thanks

[94F450SD]

Originally posted by bh2285
Yes decked is the proper lingo .
you got it backwards."decked it haveing the block milled to bring the gasket surface closer to the top of the piston.

"plane" is haveing the head shaved down.

[premiumtommy]

Originally posted by FoxMxRiders

Here the futur mods :


thicker head gasket
decked the head to raise the compression ratio.

Do you think that's a good idea??

I dont understand why you are going to deck the head to raise compression and then get a thicker head gasket just to put the compression right back where it was....

I hope you meant a thinner head gasket...

And if you are going to advance the timing, why dont you just remove the base gasket and use silicone..That with a thinner head gasket should get your compression higher for $20..

[hondamanex400]

i got a wiseco piston for my 400...and only paid like $160 for 11:1 416 kit and wiseco topend gasket kit. but i did go my honda dealer to get it bored out.

[perley03]

Originally posted by FoxMxRiders
decked ... here the way you say it :D

I don't want to use a high compression piston because I have the stock one (2001) with 120psi of compression and it don't take oil.He run very good also.

Here the mods I have :

Uni Filter
Open box
Yosh slip-on
Dyno jet kit

Here the futur mods :

advanced timing +6
thicker head gasket
decked the head to raise the compression ratio.

Do you think that's a good idea??I dont want to run on racing fuel ... do you think I can have trouble running at 91 octane? and with the headstuds?!?

When you say .025 thats is in mm then 0.001" ??

you said that you dont want to spend alot of money....a higher compression piston kit is going to run you just as much as haveing that head planed.....plus you are proballly going to run into trouble with clearances on the valves...you know, valves open and piston comes up and slappes valves and the next thing you know you got a bad problem on your hands. if you get a higher compression ratio piston the manufacture already recessed room on the piston for valve to piston clearances. i would do alot of homework on this topic before i tackle anything extreme like this.

[FoxMxRiders]

sorry my mistake ... a thinner gasket

Yeah I will think about a rebuild beside doing this modification

Thanks to all that answer

[JOEX]

The advance key and increasing the compression will most likely require higher octane fuel.

If you decide to get more into the motor decking the cylinder may be a good idea to get the proper 'squish'. Please don't ask me how to explain 'squish':p

The 400ex has a huge deck height, something like .070" I think. I don't remember all the numbers :ermm: but getting to the ideal squish can be done by using thinner head gaskets, no base gaskets and/or decking the cylinder. There could be other ways that I don't know about;)

[400eXr1d3rZ]

If you want a thinner gasket, get a XR400 gasket, it will slightly raise compression.

[Daver]

Foxmxrider , arrete de niaiser avec ton planage de tete , tu veut plus de pouvoir, **** ca la!! ca vaut meme pas la peine , va voir une machine shop et fait percer ton cylindre 426 et achete toi un piston JE ou Wiseco 11:1 de compression ca va te couter au max 200$can tu va voir une enorme gain de puissance et tu va pouvoir continuer a gazer au super !!

[Daver]

ou bien prend ton gasket de tete stock split le en 3 et prend un des 2 plus mince , nettoie le et peinture le avec une mince couche de peinture a moteur et retorque ca la , ca t`auras rien couter et tu va avoir gagner un peu de compression !! moi j`ai fait ca sur un JE 426 11:1 et j`ai fait un gasket de base plus mince.

[cals400ex]

i would also get a different piston. it will not only be higher compression but it can be stronger, lighter, and have more advanced technology. we always run a higher compression piston with a cosmetic thin flexsteel headgasket and no base gasket with hondabond on the base.