400ex cylinder/topend

[crablaster]

i am putting a 440 national kit in my 400ex i am taking my cylinder out to JB racing this weekend for them to bore it to a 440 can someone give me directions on how to take my cylinder off i dont want to mess up

[ogre]

If you dont know anything about working on one id let a professional do it. I know carb, seat, filter box. Someone who kows what there doing can do it relatively quick and probably wont cost that much more

[wilkin250r]

I'd agree. This isn't like pulling your seat off. This is the heart and soul of your quad, it's powerplant. Minor mistakes can rob serious power, and serious mistakes cost ungodly amounts of money to fix.

You don't have to be a rocket scientist to work on your quad, but you can't be a complete goof, either. If you don't know, get help from somebody who does (real help, in person, not just words on a computer screen), or else pay a professional to do it for you.

[123patrickquad]

ok look here i had no clue when i started eather so do this go buy a manual and take your time, dont be afraid to ask questions. and you have to have some meachanical abality and tools. thats about it, the only thing i had problems with is the timing. after i got the hang of it and i enjoy it, now people pay me to work on there bikes.

[dunatic564]

you have to be watch how high of compression your piston is. If it's going to be higher than stock you might want to o-ring your cylinder. I have seen a lot of 416/426/440EX's blow head gaskets. The shop I go to started haveing his machine shop put a groove on the top of the cylinder and then they use a really fine piece of wire for a o-ring then put the head gasket on top. You have to have a machine shop that knows how to do this mod. The shop I use is in Mesa, Arizona and it's call Custom Cycle. This is the only shop I have seen(might be others I just use this one) that can keep high comp 400EX's from blowing head gaskets. I have seen, played on, worked on, alot of 400EX's and they loose alot of there honda reliablity when they are turned up, so make sure you do it right. The 400EX I have right now I bought blown up(Head gasket went bad and then rings and sleave. Even though I love 400ex's if the 400 is not fast enough for you then I recomend looking in to another quad, the 400 I have now has a $2000(you will end up spending about this much) motor in it(thats blown up). If you add in the amount that you could sell a clean 400 for($3000), take your $5,000 and buy a 450r, YFZ or Z400. The YFZ an 450r are so much faster, against even a fully built 440EX. In the dunes my 400ex friends have to watch while the 450r's, YFZ's,Raptor700's and ATK's(will check out the Z450 next week) race each other. The only quads they can race are 400ex's and z400's