Piston,Cam, install for 400ex

[sandshots]

Ive been searching and cant find a How to guide on
installing a piston,and cam for a 400ex.

i'll be attempting to do it on a friends bike.
anyone want to recommend a piston,cam,exaust?
its for trails/dunes.

[EX LONERIDER]

me personally, i have used wiseco al the time and have had nothing but good results from their products.

i did my 400ex 440 kit with theirs and its nice. good quality stuff and wont dent your wallet that bad.

as for a guide, i would look for a clymer's manual. real cheap at 13 bux and very useful. read the sections on what you are about to do all the way through. sometimes even twice. it'll help out a great deal to know what you are getting into.

good luck!:D

edit; i just noticed your sig sais you are in socal......... what part? i may be able to lend you guys a hand and lend you the book.

[hypersnyper6947]

Originally posted by EX LONERIDER
me personally, i have used wiseco al the time and have had nothing but good results from their products.

i did my 400ex 440 kit with theirs and its nice. good quality stuff and wont dent your wallet that bad.

as for a guide, i would look for a clymer's manual. real cheap at 13 bux and very useful. read the sections on what you are about to do all the way through. sometimes even twice. it'll help out a great deal to know what you are getting into.

good luck!:D

edit; i just noticed your sig sais you are in socal......... what part? i may be able to lend you guys a hand and lend you the book.

I think he nailed it except my clymers was like 30. I had never even seen the inside of an egine before, with this sight and that book i rebuilt the whole top end my self, not counting machine work of coarse

[sandshots]

im in sylmar where the 210&5 fwy meet.

i see that the hotcam stage 2 and 11.1 compression piston is popular for these bikes.

how about a rev box and full exaust system. whats a good one?

[EX LONERIDER]

must agree.... this site is a BIG help as well. info on builds are so abundant here that its like picking out an ice cream flavor.... so much to be learned.

the 11:1 piston and stage 2 cam is what i did and i love it. i have a duncan racing exhaust on my bike. it makes some good power and not overly loud. you can see the mod's list on my sig.

i have it restricted right now through filtration but even restricted i still had to gear up cus i ran out of gear quick :D

[sandshots]

this one is still gonna stay stock bore. still go 11.1?

[Honda#4]

I think he nailed it except my clymers was like 30. I had never even seen the inside of an egine before, with this sight and that book i rebuilt the whole top end my self, not counting machine work of coarse


I went through the same and I could'nt had done it without using a Clymer Manual, well worth every penny.

[katch26]

Originally posted by EX LONERIDER
i have it restricted right now through filtration but even restricted i still had to gear up cus i ran out of gear quick :D

what gearing did you go up to......new to 400's and mine with the same mods but wb pipe tops out 5th really early

[EX LONERIDER]

this one is still gonna stay stock bore. still go 11.1?

yea.... that'd be a definate improvement if yer gonna stay stock bore. thing is i think you'll have to mix in race fuel or run somewhere around 100 octane to keep it from ping'n.




what gearing did you go up to......new to 400's and mine with the same mods but wb pipe tops out 5th really early

i whent back to stock..... 15/38. i was running a 14t counter and just ran out of gear really fast..... i still think i may have to go up to a 16t counter. ill find out this season.

[justin1022]

if your gona do a cam swap a easy way not to worry about timing it is to zip tie the cam sproket to the chain once you loosen the too bolts of coarse other wise you cant turn it around to get the other bolt. for a rebuilt i would def get the clymax book helps out alot only probly i had was witch rings go were when i did my 440 because i didnt have the mocromeeter. (top rings)

[hypersnyper6947]

Originally posted by justin1022
if your gona do a cam swap a easy way not to worry about timing it is to zip tie the cam sproket to the chain once you loosen the too bolts

Thats what i did too, just remember the lobes on the cam are facing down when you put it back together, assuming your at TDC

Do the 11:1 you wont need race fuel, i run premium and octane booster. You loose some of that compression through the stage 2 cam anyways. The guy tuning my quad right now told me not to worry about race fuel and he's a professional motorcycle mechanic, he said just run premium.

Buy your clymers now its the best investment you can make in this rebuild.

You may not be able to stay stock bore, to get the fresh hone and correct tollerances you might have to bore to a 86mm piston. Make sure and take that into account when buying your new piston? Im rebuilding my friends raptor 660 right now and we had to up his to a +1mm bore. I think you can go by .5mm too if you want. so he has a 101mm piston now HUGE compared to my 89mm.

[rob_990]

How about a rev box and full exaust system. whats a good one?

White Bros rev box and hmf sport series exhaust.Its cheap and it performs and sound awesome.

[scuzz]

I had the HMF and loved it.

I don't have any experience with the others though...

My rev box cam with the cam.

http://i82.photobucket.com/albums/j254/gwwaddle/400EX/100_4994.jpg

[hypersnyper6947]

sparks x6 full exhaust, dont worry about rev box it just lets you rev higher and these engines dont make power in high rpms

[scuzz]

Originally posted by hypersnyper6947
sparks x6 full exhaust, dont worry about rev box it just lets you rev higher and these engines dont make power in high rpms


Not true, it depends on which cam you get.

[hypersnyper6947]

Yea it does depend on the cam but that extra 1000 rpm is still not going to be that big of a deal. I can tell you i never bounce my quad of the rev limiter. And four-strokes generally make there power lower. Save your money from the rev box purchase and get yourself a nice full exhaust, like sparks

my friend did a 440 stroker and a stage 3 cam and it pulled off the bottom so hard and it flew up top pulled the higher gearing and extra rpm like it was nothing. Unless you have something like that its not worth the money to buy a rev box

[scuzz]

Originally posted by hypersnyper6947
Yea it does depend on the cam but that extra 1000 rpm is still not going to be that big of a deal. I can tell you i never bounce my quad of the rev limiter. And four-strokes generally make there power lower. Save your money from the rev box purchase and get yourself a nice full exhaust, like sparks

I've done it lots drag racing. :(

[justin1022]

Originally posted by scuzz
I've done it lots drag racing. :(

cuz ur shiftin to late charts show the 400ex stops making power at about 6000 (somewere around there)

Originally posted by justin1022
cuz ur shiftin to late charts show the 400ex stops making power at about 6000 (somewere around there)

6900 - 7200RPM is generally where the peak power is

[hypersnyper6947]

^ which is still low enough to not need a rev box, plus revving your engine that high puts a lot of stress on things, i like to keep mine low. Especially if you trail riding you need that low end torque, not the high rpm drag racing hp.

[justin1022]

ya rev boxes only help out for 5th gear wheelies other then that i think there a total waste i can switch inbetween my stock and stage 2 amr and dont notice anything exept with one i can pull up in 5th and the other i cant. (440 12.5:1)