is boring ur 400ex to 440ex a good idea and do u need to jet your carb.? do u need to buy a new carb.

 

Not a good idea 440's blow head gaskets and overheat.I don't know about carbing I suppose you would have to jet it if you added an exhaust...

 

I know some people bore it to 440 and then add a 450r carb, but as scrambler400 said they do tend to blow gaskets and overheat, so this is not a good idea at all.

 

i talked to several shops & they advised me against it , besides it blowin head gaskets thets the max u can take it & u would have to get another jug if it ever blew up , they recomended the 426 kit( they told me it would eat a 440 all round& they said 440 is good for playin on , not for speed)but thats just what they said , idk

 

just buy the 450 kit that comes with a new head pis. every thing you need and that not a bord head that is a brand new head and yes you have to jet the carb for the more suface area you will have so that what i would do

 

how much does that kit hit u for, since its got new everything

 

i think it is around 500-600 dollors witch not to bad for what you get

 

440 is too big for a air cooled dry sump engine! i have a 426 that new 450r's sweat to keep up!! if you like your 400ex feel, just put a 450 engine in the frame.

 

i had the shop order me the 426 kit and they had it bored , after i got it together i checked it & they had ordered me the 416 kit by mistake, i was expectin more power , but i still got some bugs to work out ,i got my piston kit for 160 +60 for the bore , they told me that for a 440 piston & ent off to get sleved would cost bout $500 , so that would b a good deal , but i believe ill try to get a 450 before i go with the 440 ,but thats just me

 

Well if pretty obvious that all of you are solely against the 440 kit. [img]i/expressions/face-icon-small-smile.gif[/img]

However you may want to explain that since you are jumping from a 85 to 89 mm piston does make a big difference in the heat factor.

It also depends how you drive it as well.

I had the 426 prior to my rebuild and it ran just as hot as my 440 kit now

as far a price:
440 namura piston: 87.80
440 namura sleeve: 55.00
shop work for resleeve: 170ish
440 namura top end gaskets: 38.00

Total: $350

doesn't sound like a bad price for a rebuild w/ all new parts...( this is you doing the work for the most part)

I will say though that you should consider the edelbrock carb #3027 for easy of tuning and for a real performance increase.

It comes prejetted so all you have to worry about it is the ideal screw and needle size and height ( everything comes w/ it)
all you need is one wrench and a screw driver.

and to tell you the truth w/ the 440 kit / edelbrock carb / cam and exhaust
ill probably put it up to any lightly modded new 450.

so i wouldn't completely rule out the 440 kit
i can't speak fully since i just got my bike together a few months ago but like i said i'm pretty happy w/ it.


i did a quick search and the 450 to 400 frame has been done.... many parts have to relocated and or new mounts fabbed.... frame has to be strengthen as well as merging the wiring harnesses... i would find it very hard to believe that it would be plug and play.

at this point i would just drop the 440 kit in.

it you really think that the 450s are all that then just save you money and pick one up....
- yes they are liquid cooled and if a big bore kit was dropped in; it would handle everybody's heat issue complaint better that the 400s could.

anyways

happy wrenching....