i am looking in to haveing a bore kit put in to my 400ex. what i want to know is what size bore should i get and what is the normal cost to have one installed

any help would be great thanks!!!!

 

I dont know the actal bore size, but search 440, thats what the big bore kit for the 400 is. never rode a bige bore 440 but I know a BB stroker 460 is FUN

 

i know what kits there is but i want to know whitch one is the most relyable and works the best

 

that might have been what you wanted to know but if you look at yor question above, it aint what you asked?

 

i would look into a 416 (87mm piston). when you match that with a cam and a good exhaust system then the gains are pretty impressive.

 

would a 440 really be any more $$$ than a 416? I know heat might be an issue and you dont want the walls to be too thin, but back when what Im riding now was a 440 it handled running all day in the heat of the dunes....

and if youre gonna be spending the money why not go big?

 

thats what i figured

 

What all is involved in doing the 440 big bore? I mean obviously you need to take the cylinder off, how much more of a pain in the *** is it than say, a 2-stroke? Can you do it with the motor in the frame? The cams are in the head so how much more difficulty does dealing with the timing chain add? What other stuff is involved, ie. carburetor, exhaust, ignition? And finally, as if you actually thought this question wasn't going to be asked, roughly what are the power gains of this? Would it be wise to create taller gearing when it's all said and done because it will have significantly more power to pull it?

 

well, I cant really answer that question cuz Ive ridden stock 400's and I missed out on this one as a 440, its now a 460 and I ride it, strokers have torque, so I know it isnt that fair to compare the two but in the sand on 21" geckos it was running 14/38 and 1st-4th had no problem lifting the front. now I have it at 15/36 but its only on 18's, there is nowhere near a lack of pull though, I bet I could pull a higher gear with 20's on it, but the case saver wont allow anything larger than a 15t and with a 36 on the rear the chains adjusted as far out as it can go and I dont have a master link right now and have been lazy so I havent gotten one.

also its not a 460 with a stock head either, its been P&P and cammed so its a far cry from just a BB on a stock 400.

 

I have a Namura 440 big bore kit in my 400ex and so far I love it!! I have ridden it 4 times since I did the work and have had no problems.....I did all of the work myself with the exception of the actual boring,,, but I have been a mechanic for the past 9 years .... It really was not hard to do at all , the hardest part was getting thecam back in (and that was still pretty easy).....I think if you are the least bit mechanicaly inclined you could do it ,, or you could pay someone around 400-800 dollars to do it for you....I had mine bored to a 416 the first time and I could not realy tell tomuch of a difference... but this 440 is amazing!...Its a torque monster!!! if you do it yourself just stay organized, CLEAN, and use common sense and you will be O.K.
Matt