440 or 426?

[400exmxracer]

I'm planning on making my 400ex an mx racer this fall/winter. I am trying to decide between a 440 11/1 or 426 11/1.

Ive heard a lot of questionable things about the 440 over heating. And I plan on really building this motor from top to bottom.

Is there a big difference between the 2? If everything else in them (cam, carb,pipe,etc.) Is the same? Thanks

[Zakradu398]

There isn't going to be much difference between the two. If I were building a 400ex mxer. I'd go up one bore from whatever it's on now and do 12.5:1 piston on race gas.

Or of course a FST 500cc stroker :devil:

[Stickman400]

I'd deff. do the 426 11:1 for an mx quad, and with the cam, carb., pipe and maybe some head work it would be a beast. Wayyyy better than a 440, especially on an mx track.

EDIT: If you want to/can buy race gas then go with a 12.5:1, other wise go with the 11:1 to run 93 pump.

[400exmxracer]

Ok thanks for the suggestion. That's what I've been thinking of going with. I though I would just ask and see if anyone has a good reason to swing my decision. And I was planning on doing a port and polish to it and maybe a 3 angle valve job.

And I do have race gas around but Id like to try to run 93 cause I'm 17 and couldnt really afford to practice :s. Could I do like 11.5/1 and mix the two? Or would that not really work?

[400exmxracer]

And how much more power is a 12.5/1 pushing out then an 11/1? Thanks

[dxcody]

Originally posted by 400exmxracer
And how much more power is a 12.5/1 pushing out then an 11/1? Thanks

No one that i have ever heard of makes an 11.5:1

But on the other hand, the 12.5:1 will make a decent sized difference in the power. I dont know they exact numbers, but it would probably make around like 10% more horsepower.

I dont know, thats just a guess. HOwever, you could do a 12:1 stage 2 cam and probably get by with a 50/50 mix of 93 and race fuel.

As long as your jetting is spot on, and maybe have some type of aftermarket cooling system.

[Pittsburgh400ex]

11.5:1 is oddball but definately possible. Can mill a few thousands off the bottom of the head and make just about any.comp. number.you want. Its done on my 450.

[JOHNDOE83]

I MX raced my 440 with stock shocks and I was way faster then any 400ex at the track, I beat alot of sposered 450r riders to.

It was fun to see them mad as hell that a 400ex with stock shocks gave them a lesson in riding.

I got hurt alot riding like that though.....:chinese:

Really though a 426 with the same rider might do just as good.

[CJM]

Power is a moot point if it dont handle. You wanna race MX at the very least you need an extended axle and +2 a-arms with the shocks and linkage correctly setup.

You want it to handle like its on rails, thus better handling the faster you can go.

Bore size is also relative. High compression makes your power not huge bore size. Does bore size give you noticeable power over stock, yes but not an insane amount.

11:1 or 12:1 piston (11;1 will run pump gas, 12:1 needs a mix of pump/100+ octane or straight up 100 octane. Stage 2 cam, right gearing and tires and the right suspension setup and you will fly.

[400Trooper]

Originally posted by 400exmxracer
I'm planning on making my 400ex an mx racer this fall/winter. I am trying to decide between a 440 11/1 or 426 11/1.

Ive heard a lot of questionable things about the 440 over heating. And I plan on really building this motor from top to bottom.

Is there a big difference between the 2? If everything else in them (cam, carb,pipe,etc.) Is the same? Thanks


I have a 440 that is crazy modified! If you can think of it it has been done. Full FMF exhaust port and polish / +1 kibble White valves In and EXH. 450R timing chain, 450R carb, etc! Fan cooled as well and I live and race in Arizona.

My personal suggestion......spend your money on suspension! Long travel +2 or +3 A-arms, long travel shocks, I prefer Fox or Elka. Get a adjustable rear axle and Long travel shock. Also a steering stabilizer!

Once you have a real suspension, be sure to have a QUALIFIED guy to set it up for you, then watch how much faster you'll be. IF you still think you need more power, go from there!! TRUST ME ON THIS!!! SUSPENSION is the winning ticket!!!!

Best of luck!!

[dxcody]

Originally posted by 400Trooper
Once you have a real suspension, be sure to have a QUALIFIED guy to set it up for you, then watch how much faster you'll be. IF you still think you need more power, go from there!! TRUST ME ON THIS!!! SUSPENSION is the winning ticket!!!!

Best of luck!!

Aint that the truth!

Too bad its the most expensive thing on the quad!

[400exmxracer]

Thanks. Do you have any other suggestions? Or tips?

[Ruby Soho]

i had a mild built 440. never ridden a 416 or 426, but i can say i loved that 440.

so my vote goes 440. you wont be disappointed in it if you do it right.

[400Trooper]

Originally posted by 400exmxracer
Thanks. Do you have any other suggestions? Or tips?


What would you like to know?? Ask away no question is dumb, not asking for as much info you can get is dumb!!!

[400exmxracer]

Alright thanks. Well i ended up going with a 11/1 426 with a hot rods crank and a fmf power bomb header and a big gun EVO r slip on with a stage 2 hot cam fcr 39mm carb a hinson clutch basket and dirt digger clutch and a crf 450 cam chain, hd head studs, a manual cam chain tensioner, hd valve springs, and I plan on porting and polishing the heads and maybe doing a 3 angle valve job. Any other suggestions to make ot faster?

[400exmxracer]

Alright thanks. Well i ended up going with a 11/1 426 with a hot rods crank and a fmf power bomb header and a big gun EVO r slip on with a stage 2 hot cam fcr 39mm carb a hinson clutch basket and dirt digger clutch and a crf 450 cam chain, hd head studs, a manual cam chain tensioner, hd valve springs, and I plan on porting and polishing the heads and maybe doing a 3 angle valve job. Any other suggestions to make ot faster?