YZ426 engine or built 400ex engine?

[trailrider894]

Hey guys, i am wondering which would be the smartest decision for racing MX? I really want something with some power that other people just don't have. I was considering a YZ426 hybrid, or just building the engine i have now. Which will be cheaper? and the best for mx?

[CJM]

Probably 500 bucks to mod the EX the way you want it, making a hybrid could be alot more to make it all work right.

[Ian400ex]

Originally posted by CJM
Probably 500 bucks to mod the EX the way you want it, making a hybrid could be alot more to make it all work right.
+1

[ish416]

I would lean towards the yz426 as stock, they will put out as much or more power than a fully built ex engine will.

By going with the yz426, you will need mod the frame, get a radiator, exhaust and a few other things.

It all really depends on how much you can find a yz426 engine for and if you will be doing the work yourself.

It looks from your sig that you have a stock internal EX. I'm not sure what class you are wanting to run but, to get an EX to run with a stock 450 you need to do the following. 87 or 88mm piston (416 or 426) running at least 11:1 compression, 04 - 05 450r carb or an FCR, a cam, HD head studs.

Also, with that kind of compression, you will probably want to get rid of your sparks timing key as you will most likely have knocking unless you want to run race fuel.

[beags86]

i have one thought on this as far as any hybrid goes. most hybrid conversions take a fair amount of fabrication.

a 440 build has is more of turning wrenchs and internal engine knowledge.

can you weld or know a welder to help you out for cheap?
can you think out of the box to come up with solutions for problems that you will encounter with put an engine in a chassis it's not designed for?

if so hybrid is for you.

now on the other hand....

do you have alot of internal engine know how?, would you rebuild it yourself or pay a shop? do you have a shop around you that you know you can trust and will stick to their word?
are you good at turning wrenchs?

also would you keep the 426 stock? would you be willing to sacrifice the reliability of the 400 for a high compression 440?

not going to tell you what to do, just some food for thought.

(for all you argumentative memembers out there, i know 440 can be reliable and blah blah blah)

just some food for thought

[trailrider894]

I am very very good at turning wrenches i have re-built several 450r's and dirt bikes before. I restored my first car by 17. lol I would do all the work myself. I feel very familiar with the inside of a 400ex. I would probably do some work on the 426 if i got it, and it would not be stock. Not sure if i would be willing to do a 440 kit. Maybe a 426ex stroker, is there such a thing?

[ish416]

I guess you could run a +4mm stroke on a stock bore EX and have 420cc never heard of anyone doing that but it should be possible. Could also run an 86mm piston with the +4mm stroke and have 430cc.

Either way you went with the stock EX engine, it would still not make as much power as a stock yz426f engine. A stock yz426f will pull 46 - 48 hp in the bike, so probably 43 - 46 in a quad with a better flowing exhaust than the stock bike.

There will be a lot of fabrication in doing a hybrid but it will be unique and completely worth it when done correctly.
Or, go the safe route and crack open the EX engine install some new parts and put it all back together.

Personally based on my own fabrication skills, I would not do the hybrid until I consulted with someone who has done it.

[250x_kyle]

hybrids make nice power when done corectly. if you dont have any experience with fab work or dont know anyone thats is maticulous with their fab work i wouldnt go with it. another thing is you are more then likely going to have to run open class with the hybrid. it you can find a 400ex jb racing modded hybrid frame i would go with that. look on ebay.

[m36indiana]

i have a 400ex frame that had a yz426 in it id sell cheap