I want to end this question.

[yellow400ex05]

Ok well I want to race MX, and I told my local mechanic that I wanted to run a 426 kit with 11:1 compression piston with HD head studs, but he told me I should go with a 416 kit 11:1 compression and HD head studs and a FCR carb, and want the 426 so I know I won't get hammered by the 450's, I dont want to get a 450 I just do't want to get smoked by them either..

He knows the kind of power I want and thats faster revving harder hitting, kinda like a 450, since I know I'll never totally replicate a 450's hit of power, and he told me I could only go so far with a 400ex before I have problems, and thats why i originally thought a 426 would be fine since its basically right in between.

[honda300EXtreme]

thats odd because the 426 is a very reliable kit and i have heard very few problems about them... if you build the 426 properly it should have a good bit of power,,

dont get me wrong the 416 is a good kit also but between those 2 kits you'll need a well built 426 to even come close to a 450...


and since your going with HD studs and a 11:1 piston it should be very reliable,

[400exrider707]

Are you planning on resleeving for the 426? That could be why he steered you towards the 416.

[zrpilot]

In my opinion your power increase will come from the following in this order:
Compression
Cam
Exhaust
Carb/intake
Displacement

So you would make more power with a 426, but not much. I'll bet less then 2 HP. A well built 416 will keep up to a STOCK 450. If the 450 has some mods, it will be a different story.

[REDRIDDER]

In my 426ex i have all the below in my sig except for the 39 tooth rear i have on the 38 with a 14 in the front and the power is amazing it feels totally different like a new quad.I how ever only have about 1 and 1/2 hours on my rebuild and about 9 hrs to go before i will start pounding it hard.My 426ex has a sleeve in it from LA sleeve to help it run a bit cooler. By boring the stock sleeve you will be leaving it so thin i dindt want to chance it.Im also impressed with the low end all the way to the top, in 5th i will hit the rev limiter if i was to hold it and it will get their quick.I have also got a 15 and a 16 tooth sprocket i have yet to try.Im running 20x11x9 irazors and yes a hot cams stage 1 that's right a stage 1 it just has the low to mid i like and it gets to the top end quickly but this maybe because of the 14 tooth sprocket but i will be trying the other 2 and i couldn't be happier my set up is for mainly the woods and tight trails.But to summ it all up if i were you id get a 426 do your self a favor get a new sleeve to ensure reliability and i don't have HD head studs but we will see if i need them or not lol...You will love this kit its just awesome power i love mine its hard hitting and accelerates quick.

[svahle]

Originally posted by zrpilot
In my opinion your power increase will come from the following in this order:
Compression
Cam
Exhaust
Carb/intake
Displacement

So you would make more power with a 426, but not much. I'll bet less then 2 HP. A well built 416 will keep up to a STOCK 450. If the 450 has some mods, it will be a different story.

I generally agree. The order might be debatable, but that is not the point. The point is displacement is often not the determining factor. I have know 416s that beat 440s across the board. I have known 416s to beat 426s across the board. It all gets back to the engine builder and the other components used. What stage cam do you have? What is your exhaust? Is there any port work? What is the compression? What is the gearing? What kind and size of carb? What kind of rev box? What kind of air filter set up? Etc, etc.

I am not putting down the 426. I think it can be a great option. But I would focus on the other factors also. Don't get too caught up in displacement. ;)

[honda300EXtreme]

Originally posted by svahle
I generally agree. The order might be debatable, but that is not the point. The point is displacement is often not the determining factor. I have know 416s that beat 440s across the board. I have known 416s to beat 426s across the board. It all gets back to the engine builder and the other components used. What stage cam do you have? What is your exhaust? Is there any port work? What is the compression? What is the gearing? What kind and size of carb? What kind of rev box? What kind of air filter set up? Etc, etc.

I am not putting down the 426. I think it can be a great option. But I would focus on the other factors also. Don't get too caught up in displacement. ;)

very well said,, and yes there are some badass 416's out there that are pretty dam fast..

[GPracer2500]

Between what zrpilot and svahle said, I can't think of anything to add. Well done [thumbsup].

[400exrider707]

All I will add is dont forget to put a CRF 450 cam chain in while its apart, very important for the reliability of that motor.

[chad502ex]

our 426's using the JE piston can hammer 48hp on the dyno... most 450R's are 45-55hp range, so I'd say that would put you in thier range...

in my experience, the 426 revs great and out powers the 416 too..

hope this helps.

[honda300EXtreme]

^^ dam,,

i think is he takes the same principles as you guys said for the 416 kit and uses a 426 bore, he will see some awsome power gains,, and as chad said it should outpower the 416..


but if he doesnt want to resleeve the 416 will be more than sufficient in the power department...

[JOEX]

Originally posted by chad502ex
our 426's using the JE piston can hammer 48hp on the dyno... most 450R's are 45-55hp range, so I'd say that would put you in thier range...

in my experience, the 426 revs great and out powers the 416 too..

hope this helps.
Remember, that's your 426 builds, not the average home mechanic:D

Is the 48hp an average number for you builds and can you get similar numbers from a 416?

[firefighterjosh]

My 416 with XC cam, JE piston, vavles, full HMF exhaulst, it runs just a tad rich which is fine. keeps up with a piped 450 till I run out of gear. My front tire is normaly right with his rear tire. Just depends on the jump I get.

Now on the track depending on surface, he clearly has more tourqe then I do. he can really lug it around the corners and come out screaming.

[chad502ex]

Originally posted by JOEX
Remember, that's your 426 builds, not the average home mechanic:D

Is the 48hp an average number for you builds and can you get similar numbers from a 416?

416's are in the 42-44hp range..

[DEVINF450R]

If you wanna go faster on the MX track get some good suspension before motor work. motor only needs to be there on the holeshot and corners, w/o good suspension that power DOES NOT HELP!

[JasonP]

bigger the better and the more power it will produce.

[krt400ex]

i say stay with the 416. you wont get all too much out of 10 more cc, and when you need to rebuild again in the future, you can go to the 426

[mxduner]

Originally posted by DEVINF450R
If you wanna go faster on the MX track get some good suspension before motor work. motor only needs to be there on the holeshot and corners, w/o good suspension that power DOES NOT HELP! i couldnt agree more.When i raced an ex i ran outta powerso i tweeked the motor with just little things and then i ran outta suspension real qwik.you will need to do both to be even close competively to the 450s.

[Fast350ex]

The 426 with JE 13:1, hot cams stage 3, john Deer tractor head studs, HD connecting rod, Curtis Sparks exhaust and clutch w/ hinson basket will smoke a modded 450. That is if you want to spend the dough. But, like stated above, you better have the suspension setup to backup the power.

[h400exrydr]

well i had a 03 416 ex with 11:1 piston, stg2 hot cam, kibble white valves, port polish, '02 CRF cam chain, yoshi full exhaust uni air filter and jetted perfect and my 450r back when it only had a pipe would just pull the 416. the 416 had more until around end of 3rd- beginning of 4th. just my $0.02. they r both killer reliable too!