z 400 jetting suggestions?

[dirtman91386]

03 z 400....putting a hmf full exhaust on it...any suggestions for jetting?,,,,can i expect big hp gains?....is there a cam mod you can do like the yfz450 but on a z 400? thanks!!!

[cataway]

Originally posted by dirtman91386
03 z 400....putting a hmf full exhaust on it...any suggestions for jetting?,,,,can i expect big hp gains?....is there a cam mod you can do like the yfz450 but on a z 400? thanks!!!

160-165 mj , 25 pj , i will also suggest you get a needle that can be adjusted, a trx400ex air boot is a good thing to do 2-3 hp.

34-36 hp


no nothing so simlpe as what the YFZ trick will do ,you really need to replace the cams , hotcams work good

[dirtman91386]

i can not find an adjustable needle....our local dearler is verygood about if they dont have it they can atleast tell you where to get it ....any suggestions where i can get the adjustable needle?...and what exactly is the 400ex carb boot?....please explain.....thanks for all the advice man appreciate it alot!!!

[cataway]

i will have to get back to you on the needle

this is a stock ltz boot (L) next to a trx 400ex boot (R)
the ex boot flows better , got me all most 3 hp, you do have to mod the box or at least raise it up and cut a 1/2 '' or so off the bigger end , all easy stuff. if your putting it to a stock carb DO NOT cut the small end. if you have a FCR carb ,do cut the small end and the big end
http://i44.photobucket.com/albums/f9/cataway/9-21-2007LS027.jpg

[dirtman91386]

ok i just installed the new hmf full pipe and put a 165mj and 25pj in it and it sounds amazing!!! but however i have a problem...you wind out first grab secound take it about 1/2 throttle and it starts to puke out....it sounds like it is hitting a rev limiter...and the higher gear you go the less acceleration you get with the throttle....

[cataway]

is the lid off the air box?

[dirtman91386]

you are a genious!!!! thanks so much this thing rips now and sounds so healthy!!!

[cataway]

this pic should give you an idea of what the ex boot looks hooked
to the box
http://i44.photobucket.com/albums/f9/cataway/P1180021.jpg

it would of been better if it had been shorten but it does work ,
getting the bumps out of the air box will alow you to put a bigger
air filter on, i used a heat gun and a stick to push/moddle the bumps out .

[cataway]

http://i44.photobucket.com/albums/f9/cataway/9-21-2007LS013.jpg

[k2thej88]

so is this last pic the same box as the previous airbox and boot assembly?

[cataway]

thats what has to be done to the box to raise the hole , thats why the pic with the boot attached has the plate on it, the hole is raised almost 2+''

if you want neer free hp thats what has to be done

[dirtman91386]

just got the 400ex intake boot...should i bump the main jet up? thanks

[cataway]

hopefully you wont have to, tho i would not be surprised if you do.
mine got as high as a 172 yet i suspect i had a few more mods than you have.
the only way to know for sure is to get to a dyno with AF capacities

[dirtman91386]

i got that 165 mj in there now..maybe go up one or 2 sizes?

[cataway]

first prove to me you have to

[dirtman91386]

so if it doesnt crack and pop it should be ok....that be great if i dont have to pop in a different jet...i hope i get some good performance out of this boot....thanks for the advice man