reliability

[finsteratv]

i know to start off the 400ex is a bullet proof wheeler. im wondering which big bore is the most reliable. along with most reliable compression etc etc thanks. whats your thoughts on this?

[HondaPohl]

It seems like the 440 kit is popular. Thats what i have on mine. Works great. Runs with stock 450's. The 416 kit is popular as well. As far as preference of brand goes. Thats up to you.

[250rforlife]

go with a 416 kit. get a 11:1 pistion. get a cam for where ya ride. and ur good to go. 440s jeted properly run too hot and a hotter motor losses power. if ya get it ported and polished with a good full exhast, uni filter, u could probly get almost 40 hp.

[CJM]

Im happy with my 416, nothing wrong with a 426.

440 is ok, but seems some people have trouble with them blowing head gaskets due to overheating in alot of cases. Maybe they cant get them jetted right, maybe its to much for the poor engine, IDK.

I went with 416 cause I wanted another bore out before I need to get the cylinder redone.

Personally I think the main downfall the EX engine is it isnt water cooled. I wonder if they had a kit around back in the day that mighta offered this, you keep something cooler it runs way better.

[finsteratv]

thats why im thinking in the future to get a 416. ive heard loads of problems with how 440's overheat. actually i already have my whole build plan all layed out haha :p. just waiting to break some stuff before my first rebuild!
how many hours do some of you guys have on your 406's,416's,426's and 440's????

[CJM]

Im around at least 500 hours on mine. I dont keep track to much. I rode it every sunday for the last 6-8 months or so with the 416 setup on it.

No issues.

[finsteratv]

the only reason i havent been to huge on going to a 416 is just the thought of tking the engine out. or are you guys able to do it with engine in bike? i mean its just top end.

[CJM]

Nah you gotta take the top apart and send it out so it can be bored properly. Dont have to take the engine out of the bike at all either. Remove the upper motor mount that goes into the valve cover and the rest slides out from there.

Listen its not a huge deal, Ive worked on all kinds of stuff before but usually shied away from engines like this b/c I was worried it owuld be overly complicated like a few motorcycles I worked on.

Theres nothing to it really. Remove all the bolts and it comes off rather easy. Putting it all back together was easy too. The manual was a very valuable tool during this entire process.

Plus if you hit a snag were always here.

[finsteratv]

i live about 3 miles from motosport and im 99% sure they can bore cylinders. now that i know its not a total engine out maybe ill think on it a little more...crap...i can feel it..A.A.D.S.

[CJM]

Ha, hooked another one! Dang AADS!

You will be happy, do a full build up with it and enjoy :)

[finsteratv]

haha id love to dump all my money into my bike..the one thing i love to do is ride! i just think of how you put money in and never get it back out. ive got the money just good with my finances for 14 :D haha

[BenHonda400ex]

Originally posted by finsteratv
haha id love to dump all my money into my bike..the one thing i love to do is ride! i just think of how you put money in and never get it back out. ive got the money just good with my finances for 14 :D haha What pipe are you getting?

[CJM]

Originally posted by finsteratv
haha id love to dump all my money into my bike..the one thing i love to do is ride! i just think of how you put money in and never get it back out. ive got the money just good with my finances for 14 :D haha

Its kinda tough when your that young. For me I dont skimp on quality parts and services. When I built my topend up it cost me quite a bit:
-bore and head studs gt thunder was like 150, did both there cause they were doing the studs anyways
-11:1 wiseco piston 100
-stage 2 hot cam 100
-jetting about 75 bucks
-cometic gasket kit think it was 75, i used the best one they had
-crf timing chain, guides, gasket 150 iirc, the dang guides are $$ but worth it as they are usually worn
-clutch holder tool was 15 (to do the timing chain).

In total I think I spent 500 bucks.

[finsteratv]

i was thinking 416, with maybe a lower comp piston for now like 10.5:1 thinking i can maybe avoid headstuds for now but i know theyre definately good to get. then also a sparks x1 cam just because it seems like a good crossover cam along with a good pipe. i think before i start with engine i'll do suspension then go for it. during summer i can pull in more then enough for the building. ive paid for all my bikes and gear along with aftermarket so i can do whatever my heart desires :blah:

[AtvKid4Eva]

416 or 426 with an 11:1 piston and a hotcam is a good combo. they are both reliable. When you go to a 440 you start to loose reliability due to cylinder wall thickness and running higher compression and blowing head gaskets.

[DragonGunner]

Originally posted by CJM
Im happy with my 416, nothing wrong with a 426.

440 is ok, but seems some people have trouble with them blowing head gaskets due to overheating in alot of cases. Maybe they cant get them jetted right, maybe its to much for the poor engine, IDK.

I went with 416 cause I wanted another bore out before I need to get the cylinder redone.

Personally I think the main downfall the EX engine is it isnt water cooled. I wonder if they had a kit around back in the day that mighta offered this, you keep something cooler it runs way better.

Back in the day they did offer a water cooled cylinder for the 400EX, got it in one of my back issues....can't remember who made it, but seemed the whole kit was around 2000.00....never knew anyone that bought one or saw a test result on it....air cooled engines do loose hp the hotter they get....but in some muddy races seen some water cooled dnf...think the water cooled EX that was that issue was a 500EX....?...I keep thinking Four Stroke Tech did it....?

[CJM]

^ I did google it and yea I think it was FST and they made a 500cc monster. Apparently no one ever bought one due to the cost. It used an electric waterpump off a KTM which I thought was neat.

In reality if you want water cooled on a honda gotta step up to a 450R it seems.

[DragonGunner]

Originally posted by CJM
^ I did google it and yea I think it was FST and they made a 500cc monster. Apparently no one ever bought one due to the cost. It used an electric waterpump off a KTM which I thought was neat.

In reality if you want water cooled on a honda gotta step up to a 450R it seems.

Ya, but back then the YFZ450 hadn't even came out yet....took Honda way tooooo long...but they had a good thing with the 400EX an just laid back until Yamaha came out...if you want water cooled on a Honda gotta step up to the 450R....or put in a KTM 520 in a 400EX.