Need more power in your KFX 400... Do this!!

[CGCinc]

Holy Crap...

I bought a Yoshimura RS-3 Comp full exhaust, FMF jet kit and a K&N filter. I wanted to leave the stock airbox lid on because I plan on going to HatfieldMccoy trails in July and there is a lot of water crossing there.
Anyway, with the lid on I had a small stumble at maybe 3-4000 rpms and I couldn't tune it out with just the mixture screw so I figured it was jetted too fat and was going to change the main jet. Well, before I tore into it I decided to take the air box off just to see if more air would get rid of the problem.

OMG!!! This thing has twice the balls, sounds awesome and runs perfect with no stumble at all!!!! Needless to say, the stock air bgox is going to stay off!!

[knoxville9]

Great job and btw Hatfield can tend to be wet but you should have no problem with out it, it's a blast. I would be more worried about dust ive gone up there in april, october, and june and evertime its DUSTY and you do not wana suck that in. I would suggest cleaning your filter after everyday and allowing it to dry over night. just a suggestion and have fun!! =)

[cataway]

Originally posted by CGCinc
Holy Crap...

I bought a Yoshimura RS-3 Comp full exhaust, FMF jet kit and a K&N filter. I wanted to leave the stock airbox lid on because I plan on going to HatfieldMccoy trails in July and there is a lot of water crossing there.
Anyway, with the lid on I had a small stumble at maybe 3-4000 rpms and I couldn't tune it out with just the mixture screw so I figured it was jetted too fat and was going to change the main jet. Well, before I tore into it I decided to take the air box off just to see if more air would get rid of the problem.

OMG!!! This thing has twice the balls, sounds awesome and runs perfect with no stumble at all!!!! Needless to say, the stock air bgox is going to stay off!!
did you change your intake boot to , theres a good 2 hp for ya if you do.

i just changed mine to some thing different ,its from a ds650 ,cut to make it about 9'' long
http://i44.photobucket.com/albums/f9/cataway/PictureSL4-11-09011.jpg

http://i44.photobucket.com/albums/f9/cataway/PictureSL4-11-09017.jpg

http://i44.photobucket.com/albums/f9/cataway/PictureSL4-11-09010.jpg

i dont know if it will fit a stock carb, thats some thing i'll have yet to try.

but a trx 400ex will

[CGCinc]

Originally posted by cataway
did you change your intake boot to , theres a good 2 hp for ya if you do.

i just changed mine to some thing different ,its from a ds650 ,cut to make it about 9'' long

i dont know if it will fit a stock carb, thats some thing i'll have yet to try.

but a trx 400ex will

No I didn't.... Is the stock boot not just a round tube?
Did you have to rejet for this?

I love Extra power....!!!

[RATPACK Z400]

That looks a lot better than a400ex boot and cleaner look and more air !your carb is from 450?

[cataway]

Originally posted by RATPACK Z400
!your carb is from 450?
the carb is from a yfz 450 , tps removed and a R A T stack put on
http://i44.photobucket.com/albums/f9/cataway/9-21-2007LS061.jpg

so far its the best intake boot that i have tired and i have used the 400ex and the 450r 04-05 boot, both way better than the stock ltz

some honda riders use it to ,hard to beat the price of $ 42 delivered , but like i said i dont not know if it will fit a stock ltz's carb ,but i do know it will not fit a fcr carb unless theres an adapter like the R A T stack.

it will fit a 04-05 450r honda carb but its cut in a different place
http://i44.photobucket.com/albums/f9/cataway/Pictureutsandmt419.jpg

kinda what it looks like before its cut in half ,the silver ring is at 9''
http://i44.photobucket.com/albums/f9/cataway/PictureSL4-11-09012.jpg

[kawiracerj]

very cool guys!!!:) :) :)

[twincat800]

is that big silver square thing the r a t?? in the future im lookin to get the fcr carb and a boot

[Nick24]

I took only the lid off the air box and it would just bog out really bad if i gave it any more than 1/4 throttle. I dont know if that was because i only have the stock filter or if the carb needs to be adjusted or what.

[CGCinc]

Originally posted by Nick24
I took only the lid off the air box and it would just bog out really bad if i gave it any more than 1/4 throttle. I dont know if that was because i only have the stock filter or if the carb needs to be adjusted or what.

If thats The only thing you did then its running lean...You'll have to rejet the carb but you'll have more power And more sound!

[cataway]

Originally posted by twincat800
is that big silver square thing the r a t?? in the future I'm looking to get the fcr carb and a boot
no thats not a rat stack, thats a support for the boot and filter
the rat is attached to the carb in the first pic

[Nick24]

ok thanks for that i might have to try it agian after i adjuust the carb.

[Nick24]

Originally posted by CGCinc
Holy Crap...

I bought a Yoshimura RS-3 Comp full exhaust, FMF jet kit and a K&N filter. I wanted to leave the stock airbox lid on because I plan on going to HatfieldMccoy trails in July and there is a lot of water crossing there.
Anyway, with the lid on I had a small stumble at maybe 3-4000 rpms and I couldn't tune it out with just the mixture screw so I figured it was jetted too fat and was going to change the main jet. Well, before I tore into it I decided to take the air box off just to see if more air would get rid of the problem.

OMG!!! This thing has twice the balls, sounds awesome and runs perfect with no stumble at all!!!! Needless to say, the stock air bgox is going to stay off!!


Now when you took your airbox off where did you put your rev box at because i think it is srewed onto the air box, isn't it?

[CGCinc]

Originally posted by Nick24
Now when you took your airbox off where did you put your rev box at because i think it is srewed onto the air box, isn't it?

I just took the lid off... The box is still in place to keep water from splashing all over the filter

[knoxville9]

I've never done this before or taken my air box off at all but im a redneck so id just zip tie the cdi to the frame haha :D

[Nick24]

Originally posted by CGCinc
I just took the lid off... The box is still in place to keep water from splashing all over the filter

Ok i see

[Nick24]

Originally posted by CGCinc
I just took the lid off... The box is still in place to keep water from splashing all over the filter

Ok i see