426 ? 440 ?

[ThorR88]

im going to either do a 440 or a 426 in my 400ex im un sure of witch i want to do at this time i was wondering if any of you have suggestions about what i should do and where i can get the kits from and about how much i can buy them for thanks alot!

[Chris S.]

If money wasn't a factor, my opinion is the PC 4000 cylinder kit from duncan racing is the best. You can pick from a variety of compression ratios and displacement options. I have seen them for sale on ebay for $750 and Duncanracing.com lists them for $950 but you may want to call them. This kit includes a whole new cylinder with sleeve already installed and comes with piston rings and gaskets. Also had bigger head studs and better cooling. If your old cylinder is in good shape you can sell that for over $150.00 probably. Alot of people need cylinders or want back up ones ready to bolt on.

[CFRacer03]

If you're gonna spend the time and money you might as well go ahead a do the 440. but remember there are a lot of things that go into making power, its more than just displacement, especially head work...

[xxnightraven73x]

mine has the 440 kit in it and it compares to my 04 raptor that i had its got all kinds of power and loves to pour it on

[ThorR88]

they have a 440 big bore kit on ebay with a stage 2 cam from wb i think for like 400$ would that be alright?

[cdrookie]

some people have had problems with the 440 kits blowing head gaskets, thats why some opt for 426 and 416's. i heard C&D has a sweet 416 kit available. might want to give them a call and see what they say.

[deathman53]

don't forget no matter what you do, get a valve job and the head ported/polished and a cam.

[stupid driver]

the factors that will decide what kit benefits you the most are endless...what type of riding you do, what type of rider you are, etc. However, most of the time, it boils down to this: a well built 440 will suit a rider who loves bottom end. an engine bored to 440 has much more mass on the piston compared to a 425 or 416, so it will not rev quite as quickly.( we're not talkin much here) But here's the deal: If you buy a bore kit alone ( piston, sleeve, gasket) and just install that alone, you are not going to see much of a difference. The real gains come from the other motor work, such as porting and polishing the valves, lightening the flywheel, and all the other "good stuff."
I own a 425, and I have been happy with it. There are a lot of motors out there that will give you the power you want. Your best bet is to ask around, get some opinions on what works for people as far as the bore size goes. Myself, i only have experience with a 425 and a stock motor. The gains that the 425 gave my motor were tremendous. But ask around on this site for people who own 440's as well, and base your decision on that. Hope I helped.
Slick

[boricua]

are you looking for the pros and cons of both motors? i.e. 426 revs higher faster, 440 doesnt.....440 has more bottom end, etc. it seems like most people are responding in the way of power output. if you want to know the good and the bad of both motors.....let us know.

[ThorR88]

im looking for a motor for mx racing that will keep up if not beat the 450r's...

[stupid driver]

Originally posted by ThorR88
im looking for a motor for mx racing that will keep up if not beat the 450r's...

well... you set your stakes high i see. Heres the deal, a decently built 425 or 440 will beat a 450 IF you are equal riders. Im sure youve heard this a thousand times, but its true: the rider makes the difference. But there is one small problem...the 450 motor is much more responsive to mods than our mighty 400's. Ya, it sucks, but its true. If you expect to beat a piped/filtered 450, you better be throwin around some cash and goin for a complete overhaul.
Here's what i would do: Since your ridin MX, your gonna want a high revving machine that gets up and goes on a dime. Get yourself a decent 416 or 425 kit, and have a local builder who has a decent reputation port and polish your motor. Dont forget the other essentials like the cam, pipe, etc. THEN, take the money you save from not buying an all out racing motor, and buy a decent pair of shocks. The improved handling will translate into faster lap times; which, if im guessin right, is what you want.
Slick

[Chris S.]

Well, if your wanting to run with 450's its going to cost you. I just sold my ex and I had a high compression 440 motor fully ported with xr400 cam, 450r carb, full HMF exhaust and a 500FST stroker motor with web cab, port job, and alot of head work and neither motor comes close in acceleration to my 2006 450r with HRC kit. The only place the ex had more power was at idle. I tried with very hard with my ex motors to be faster than 450's and after spending more money than I want anyone to know, I went a bought a 450. Sorry but that is the fact and if you can get a ex to perform better than a 450 you will have a engine that isn't going to last long. However you can build a ex motor and be real happy with its performance and reliability if you don't expect to much.

[jsmith2232]

I went with the 416 due to its ability to rev faster and run cooler then the 426 and i still can go up with the stock sleeve if i want to later. If you go with the 440 kit theres alot of other things you will have to consider to make your setup more rigid. with the mods listed in my sig i can hang with stock 450s and has enough torque to do a wheelie sitting down in 5th I got the piston, cam and gasket kit thru c&d racing for 310$ and had it in 3 days and a bore job only costed 55$.

[ThorR88]

i was thinking of a 426 or a 460 stroker! that will smoke....

[Wheelie]

Strokers are more money than a bore kit.

If you're serious about a stroker kit, I highly recommend Powroll. The quality of work is first rate and excellent customer service.

Should have my cylinder and cylinder head back next week, be riding again by the end of the month.:macho

[2muchquad]

the 416 is perfect for mx imo.it all comes down to the rider anyhow,if your in shape and you can charge the whole race you could do pretty well against the 4 fiddys.you dont need the holeshot to win.;)