Tell me about your engine build (under 440)

[MtnEX]

I'm trying to educate myself a little on a possible engine rebuild.

If I'm going to do it, I want it done right.
But at the same time, I'm not going to go crazy.

I know some of you have done/had done topend rebuilds.
With what I have already, I'd like suggestions on what to go with it.
I'd also like to know what if anything you did yourself.
And what you didn't do... who did you get to do it... if I can use them.

I'm sure some of you have also had to do a complete, going into the bottom end. I'd like to learn about that too.


I'm trying to get an idea of the effort involved, the cost involved, etc.




I don't think I have a local place I feel comfortable with. I'm also thinking I would probably want to do a complete rebuild and replace everything that is needed, unless there is a builder I can trust who insures me my bottom end is SOLID still.


I want a real reliable build... a pump gas motor... I want it to be quick... lots of throttle response... but mild and torqy enough for the tight woods and steep climbs.

I'm thinking a 416 or less if possible, if it needs an overbore.
I'm thinking follow Mickey Dunlap's advice on gaskets.
Some sort of cam if needed due to wear or for the mods.
If it needs any valve work, going all out there... the whole 9.
Maybe a better carb to go with it all, if needed.
New better timing chain, etc...

[drew416ex]

I had a 416 before my 440. I did all of the work except for port and polish. It was 11:1 with no base gasket, stage 2 hotcam, ported and polished, sparks x-4, and for the first two years the stock carb with choke removed. The last year I had it it was a kehin 39mm fcr. It ran extremely well reved quick and had lots of torque. I think you would be fine with a 406 that way you would still have 2 more bores left. Over all its not hard to do a top end. I rebuilt my bottom end a few months ago and stroked it. It wasnt really any harder to do as long as you have the tools and be patient. I got my head ported at Thumper Racing in Marshall TX. Your bottom end should be good as long as you kept good oil in it. The main thing to check is the wrist pin hole on the rod. That bushing will wear out which would mean you would need the crank rebuilt or a new on with a rod.

[buck440]

no such thing as 406 only std 416 426 440 and 460 for strokers

[MtnEX]

There is a 406... I remember seeing one and thinking that would give me one more bore.

[78ta]

406 is 86mm bore stock stroke.

1mm or .040 over stock bore

[Pipeless416]

correct. i don't get why people always try to prove others wrong with incorrect info..? :confused: go for the 406, the extra 10 cc's won't make nearly the difference that the bump in compression will.

[78ta]

you need to have the bottom end checked before you waste your time on the top end, if your bottom end is worn out or close to it , a fresh higher compression piston will finish it off for you in no time.

I had about $40 in getting the cylinder bored and honed to the new piston size. Make sure you give the new piston to whoever is going to bore your cylinder so the piston to wall clearance and ring gap can be set.

I can't remember what I had in the piston kit, but you can look up prices on egay. You'll need a good quality piston, wiseco or je I would'nt go above 10.5:1 compression on an old bottom end with much time on it in my opinion. I used Honda gaskets, but cometic gaskets are just as good or better. And a new timing chain, I used a crf450 chain which is about $40 give or take. I bought most of my stuff from yamaha of troy.

You can have the topend rebuilt for somewhere around $300 if you do the labor yourself.

Top end is not that difficult if your somewhat mechanically inclined. You need to invest in a good manual and follow it to a T. You will also need a good torque wrench that go to all the correct torque specs.

follow all torque specs and keep everything clean, remove all old gaskets and replace with new, clean out all oil screens while you have it apart, and have fun getting the wrist pin cir clips in if you have never done that before...make sure you keep plenty of clean lint free rags stuffed in the bottom end while your fighting with those cir clips. You'll need an impact wrench or clutch holding toll to get clutch basket and primary drive nuts off to change the timing chain.

As for the bottom end, If your going to replace the crank, I would not suggest you try that especially if you have never done a top end job before. There is a whole lot more pieces parts and splitting the cases for your first time is not the easiest thing to do. I would leave that to a professional or someone you know and trust to do that.

[MtnEX]

Well, to be honest about it, I'd love to do the rebuild myself.
I'd like to see first-person every detail of it.

However, the big limitation I have is TIME.
I could make time for it, but it would be tough until later in the year.

I'm also nervous about it, never having done it before. Particularly checking the service limits of everything.


I also think if I'm going to do it, it only makes sense to freshen it all up, or freshen everything that needs it. I'd feel more relief doing it that way anyways.


So, with that said, is there anywhere you can just send your entire engine for a complete rebuild?

If so, how much we talking?


So far I have a single quote on that, and the total is so much that it completely makes no sense. The reason is that I know where a nearly brand new 400EX is that I can get for a couple hundred more.... I mean it's a late model but has been ridden so little it still has the little rubber thingys sticking up on the tires.

[MtnEX]

While we are talking about this... does anyone know if there is a particular adapter needed to check the compression? If so, what size?

I haven't done that yet even.

[AtvMxRider]

Originally posted by buck440
no such thing as 406 only std 416 426 440 and 460 for strokers

[justin1022]

Originally posted by 78ta
406 is 86mm bore stock stroke.

1mm or .040 over stock bore

and honda will make a pistion for you for that bore right? someome told me that they do

[Honda#4]

I finally did my first topend rebuild not to long ago and did everything except bore,hore and port the head for that I had Colby @ C&D Racing do it.

All my head work totalled around $420ish.

Motor specs

JE piston running 11:1 comp
C&D Racing Ported head
Stock Carb for now but will be buying a 450 carb soon
CRF Cam chain- any year works
Hotcam Stage 2
Stock gaskets

Getting close at dialing it in jetting wise but it has great mid to top end power with moderate lowend.

A Clymer manual helped me out alot, it does a good job at being in depth and has great wording so you'll hardly get lost reading it.

[MtnEX]

Well, as it turns out, a guy I knew of that I figured was long gone is supposed to have a pretty decent race shop now all these years later.

So.... if nothing goes wrong, I'm going to try hauling it over there tomorrow for him to have a listen at my engine... and hopefully get a decent quote.

After all that, if he can give me a good answer and I feel comfortable about it, I may let them just tear it all the way down for inspection.

I just need to get started figuring out what I want back in there part-for-part for anything that may be bad.



For pistons, I don't know of anything but Wiseco and JE?
Seems like there is another?
Size... I think I may just go with what's needed.
Compression... pump gas.

Connecting rod... hot rod?

New cam chain and tensioner PERIOD.
Chain... HD, XR or CRF?

Cam... Hotcam or who else?
Stage?... Probably stage 1 for smaller bores?

Valvetrain.... kibblewhite?

Carb if needed... 450R?

[78ta]

what are you wanting as far as power and reliability? What part of the rpm range do you want the power and what are you planning to do race, trail, play?

that would help people tell you which parts to buy and which ones to stay away from.


as far as pistons, there are many other choices: CP and Pro-X are just a few of the others. Go with WISECO or JE in my opinion, I have rebuilt about 6 dirtbike/atv's 2 and 4 stroke and I use Wiseco's in every one, never had a problem and they make good stuff. I have used JE pistons in small block chevy's for years and they are great as well. Never used them in an off road bike though. If you want to run pump gas, don't go above 11.5:1 for the best reliability.

at a minium go with .040 or 1mm over sized bore, unless there is cylinder damage worse than that or you want a little bigger bore than a 406cc, but remember that the bigger you go the worse of a chance of loosing some reliability and will tend to run a little hotter because of a thinner cylinder sleeve

as for cam chain get the crf450 dirtbike chain, it is the same as the hd chain and is a factory honda part and is cheaper to boot. I don't know about the xr chain, but I'm guessing it prob the exact same as th ex chain

If you go with the hotrod crank, I think you may have to use a wiseco piston, But I'm not 100% sure on that. Maybe someone else can chime in on that

as for valves, ti is great for racing but is not as tuff as stainless.

[MtnEX]

Originally posted by 78ta
what are you wanting as far as power and reliability? What part of the rpm range do you want the power and what are you planning to do race, trail, play?

that would help people tell you which parts to buy and which ones to stay away from.


Well, if I'm rebuilding, I want power... but not at all at the price of reliability. I want to be riding, not wrenching... and if I can't get the reliable power I'm looking for out of the EX I guess I'll have to bale out and go to a Z400 or 700R.

Myself, I do a lot of short burst play. I ride woods/XC not open desert. So I want the power to come on quick at the command of my thumb and be predictable. I also want to be able to crawl around the real technical areas with a lot of stall resistance/lugability (that's what the YFZ lacked in).

I don't want to rev it to the moon either. It un-nerves me on a 4 stroke to begin with, and secondly I don't want the power way up there.

I'll also want to build/tune "to" the exhaust system I already have. To be honest, I really don't know exactly what that would be either... because I don't know what "sort" a full Yoshi system is. I don't know what it's engineered more towards... low, mid, high?....

All I can go by is appearance and flow... seems like it has the size/volume to handle as much displacement as is possible. But past that, I don't know a thing really.

[MtnEX]

Originally posted by 78ta


as far as pistons, there are many other choices: CP and Pro-X are just a few of the others. Go with WISECO or JE in my opinion, I have rebuilt about 6 dirtbike/atv's 2 and 4 stroke and I use Wiseco's in every one, never had a problem and they make good stuff. I have used JE pistons in small block chevy's for years and they are great as well. Never used them in an off road bike though. If you want to run pump gas, don't go above 11.5:1 for the best reliability.

at a minium go with .040 or 1mm over sized bore, unless there is cylinder damage worse than that or you want a little bigger bore than a 406cc, but remember that the bigger you go the worse of a chance of loosing some reliability and will tend to run a little hotter because of a thinner cylinder sleeve

as for cam chain get the crf450 dirtbike chain, it is the same as the hd chain and is a factory honda part and is cheaper to boot. I don't know about the xr chain, but I'm guessing it prob the exact same as th ex chain

If you go with the hotrod crank, I think you may have to use a wiseco piston, But I'm not 100% sure on that. Maybe someone else can chime in on that

as for valves, ti is great for racing but is not as tuff as stainless.

I think I will settle towards a Wiseco pistion in case I have to have a connecting rod. I'm pretty sure you are right on that combo.

It will be 11.5:1 or less, and .40 over or more if it needs boring.

crf450 dirtbike timing chain it is.
Now what about a MANUAL TENSIONER v/s new stocker?


That's a few things settled and out of the way.
Helps ease my mind to be prepared for the unknown.

[78ta]

go with the stock tensioner, the manual one you'll have to constantly check/adjust and its not in the easiest spot to get to. not worth the extra effort in my opinion.

as far as the rest I think you would be happy with a stage 1 hotcam, you won't lose the bottom end torque that you will lose with the stage 2.


86mm bore
11:1 wiseco
stage 1 hotcam
full yosh exhaust

I think that sounds like it would be a very snappy and torqy. Should run pretty cool, and be very reliable as long as it is put together right.


If you want to spend a little more money, get the head trail ported buy someone that knows what they are doing

Originally posted by 78ta
86mm bore
11:1 wiseco
stage 1 hotcam
full yosh exhaust

I agree on the cam and the bore size but I would go 10:1 wiseco and a HMF or Sparks.

[MtnEX]

Originally posted by FoxHondaRider
I agree on the cam and the bore size but I would go 10:1 wiseco and a HMF or Sparks.

Why?

I already have the full Yoshimura system.

Maybe those are better?... But I already have this.. $

[78ta]

10:1 would be easier on the bottom end and little less heat and little more detonation resistant than 11:1

The reason I said 11:1 is because you will notice more bottom end power gain and little snapier throttle response. but you must use 93 octane or better to keep detonation at bay, and must be jetted correctly also. But worth it in my opinion.


depending on what gaskets you use it will prob be a bit lower compression than advertised anyway.

[MtnEX]

In this thread is a video of the reason I'm worried about a rebuild.

http://www.exriders.com/vbb/showthread.php?s=&threadid=364729

[Ruby Soho]

you dont have to worry about reliability on the 400ex if you build it right.

my 440 is pushing two years in about a month.. still no problems EVER.

you can go whatever bore youd like, just make sure you go the extra and get GT thunder hd studs, CRF cam chain and get all the right gaskets and so on. don't skimp out on the build.