426ex

[xtullyx16]

Im wondering what all do i need to make a reliable 426ex and to do it right.

[jeepthing07]

I'm currently building a 426 im new to 400ex's but from what i have gatherd you should use a HD cam chain from a CRF450 and HD head studs.

I'm not sure what piston im going to use but it looks like the best one is CP piston followed by JE piston. i think im going to use the JE cause im trying to do this cheap. im not going to skimp enough to use a wiseco though.

[Black R/T]

some people will disagree but oh well. RESLEEVE!!! 426 is the last bore on the stock cylinder making the cylinder wall thin and more prone to cracking. get a big bore cylinder and put your 426 piston in. this alone will make your motor more reliable. also, make sure you have at least .020" play between the bottom of the cylinder and your cases. do this by removing the little steel collars that line up the cylinder with the cases and then slide your cylinder in the hole and move it around. if its tight, grind down your cases or you will have a tight spot when your piston hits bottom dead center. i know im not explaining some of this as well as needed but im busy and i dont like typing. go look in the how-to section. a guy that made or makes a 505 kit for the 400 started a thread and he explains it perfectly.

[xtullyx16]

shoudl i use a crf450r cam chain or 450r cam chain? how much do they cost usually?

[blue_ex_rider]

use a crf450 they are around 40 to 45 bucks half of what a stock 400 is

[xtullyx16]

does it matter what year?

[blue_ex_rider]

02 and up but i think that is when they satrted making the crf so i guess it doesnt matter

[REDRIDDER]

As said above RESLEEVE it!!! it will be more reliable and will make it run cooler apposed to boring the stock sleeve.I sent my cylinder to LA sleeve and had them do the sleeve install.I also used the CRF450r timing chain,i did not use the HD studs and have had no problems in the year and a half or so its been together.While its apart think about changing out your valve seals and valve guides.It's also a good idea to check your valve seats.One other thing is if you go with a new sleeve you have the option to bore out the sleeve to a 440 in the future if you choose to or need to.You will want to buy a good gasket set for a 440.I love the power that my 426ex makes, its a fun bore size and it feels very torquey.I could go on and on about my 426ex i just love it and wanted something different than a 440 witch everyone has.PM me if you have any questions regarding the 426 i will be glad to help you any way i can.