big time help needed...PLEASE

[gery350]

guys i really need some input on this.

the other day i jetted my neighbors z400 and it runs awesome. so i figured i'd do the same to my sons(he has a yoshi trioval titanium)


well to make a long story short i started off with a 155 and 4th position clip and it ran like crap(granted itr ran perfect prior to me touching it)

well i worked my way down all the way to the way it was(original jet needle and original main jet) figured it was working fine before so lets just leave it the way it was.

lo and behold about 1/2 throttle to full throttle runs like crap. it sputters, no power. i did the "night test". in the dark the pipe glows red runs fine about to half throttle. half throttle to full throttle runs crappy and pipe goes dark(indicating rich at high rpm)

what i cant figure out is that i put everything back to the way it was and now it runs like crap. it also backfires on decel.

please help. i dont know what else to do.
thanks, gery

[kfx400rob]

i have a trs on my 06 kfx400 and i use third clip on needle and a 150 main jet and it runs perfect, but i think the 03 and 04 has a slightly diff carb?

also maybe the reason it runs worse the same now is if u got some dirt or something in the jet while you were putting it on cuz when i had dirt in my mainjet it did the same thing ran bad at mid to full throttle and stuff

[dynodon]

There is deffinetly something wrong ( obviosly ), check to make sure you have not bent or obsructed the floats when it was tore apart. Like said before, you might have some dirt blocking the main jet.
 Hope this helps, dont get aggrivated( just walk away for a few and then go back to it )   GOOD LUCK

[gery350]

well couldnt sllep thinkin about it.
but your right dynodon i was so damn frustrated yesterday.
what i dont understand is that wouldnt an obstruction in the main cause a lean condition cause uou'd be obstructing the fuel flow?

well gonna have a go at it again now nay further advice would be GREATLY appreciated.
 
thanks, "frustrated as heill"

[tony pitts]

need info have you done anything else . like removed air box lid cams etc.

[dynodon]

gery350, I reread your post again, are you sure you have the clip in the same groove as originally set ?? It sounds like its in the wrong groove. Check the floats again too, they may have gotten bent and not allowing fuel flow. Just a thought.
  Believe me we have all been there as well, clear your mind and go slowly, and thoroughly.

[LakeMaryKid]

I thought when there was nothing past half throttle it was running lean? Main cause of this usually is the main has fallen out and is rolling around in the bowl.

[gery350]

ok went through it again.

took the whole thing apart cleaned it all out with carb cleaner to no avail.

from about 70-100% throttle it sputters with no power and backfires on decelleration. given it takes off like arocket but dies out towards the end of the power band.  i put everything back how it was. the stock jet needle doesnt have multiple clip positions so that wouldnt do it. ive tried with/without lid/air filter, changing position on the fuel valve-nothing. man i dont know what the hell to do.

is it possible that the needle gets stuck and doesnt go full open position?

dire need of help....

[tony pitts]

without the lid try a 170 main jet  that should work well with your aftermarket exaust system  my wifes bike is an 03 and it works perfect

[kfx400rob]

the needle should be on the 3rd clip is it? if its not adjustable then its stock and u should get an aftermarket needle and id think i 170 mj is way to big i have a 150 with the same bike and exhaust as u also the air fuel screw should be 2 1/2 turns i think

[gery350]

my problem is that prior to trying to jet it it ran fine.
i put the stock stuff bak on and instead of running like it was (ok)
it wont run at 3/4 to full throttle and backfires on decel.

drivin me crazy!!!

[tony pitts]

check this site out . http://www.z400central.com/invision/lofiversion/index.php/t33116.html ive been jetting and building bikes for four years now I have or modified over 20 z400  talking over the web is just trial and error  this stuff takes time and patience slow down and do one step at a time

[dynodon]

By chance did you remove the gas tank??, Possibly the fuel line is bent restricting the flow, and possibly collapsing when its trying to pull fuel through it.     Just another thought, with out being there its really hard to diagnose it .

[dynodon]

I just talked with Cut, he says you might have a vacuum line either not hooked up, or a cracked , broken vacuum line. We had a z400 that did that to us awhile back also !!!

[klutchbuster400]

yeah i checked theres a vacuum line that goes to the fuel valve under the tank and its hooked up. the only other line i see is the breather that goes to the air box. i dont know maybe i'm missing one.

[dynodon]

Is the vacuum line cracked ?? posibly where it connects to the carb, is usually where they will crack !!!

[klutchbuster400]

no it all checks out ok. i'm gonna try again tomorrow.
dont what i'm gonna do but try again i guess..............

[cutngrs]

 first  try  putting the choke on at hafe throttle and see if it runs better 

[klutchbuster400]

man i tried that and it had no effect.

i was thinking maybe the choke was stuck but at idle it runs perfect and if i choke it cuts off indicating that the choke is not on.

i was wondering if the air channel to the diaphram of the jet needle could be clogged.

i figure that the needle rises due to a change in pressure in the diapram chamber.(hence no air to the chamber,no rise of the needle)

[gery350]

ok guys monday 2-27-06 still nothing.

took carb completely apart sprayed carb cleaner thru all air and fuel channels followed by compressed air. switched to 150 main and 3rd clip position on the needle. checked vacuum line to fuel valve and bypassed it and still nothing.

i am completely stumped. all i can think is that it has something to do with the diaphram that lifts the jet needle. it idles perfectly and accelerates great. the problem is from 3/4 throttle to full throttle(sputters and backfires on decel)

pulling my hairs out.

[gery350]

dad cant find out whats wrong, i cant ride, friends goin to the track thursday.

[KB]

try a new spark plug .maybe you fouled it when you were messing w/ the carb. ? good luck!

[gery350]

i think i'm giving up on this carb. its an anomoly.
ive completely disassembled,cleaned with car. cleaner and compressed air every chamber, hole and nothing is clogged. the problem has to be in the plastic jet needle holder getting stuck in the chamber.

i remember the old fords that came with the same carb systems that never worked right. they were called variable venturi carbs.(piece of crap)

oh well time to shop. now i'm not sure whether to go with another stock crap or look for a reasonable priced aftermarket. i mean the bike is stock so dont know if it would warrant a bigger carb and i  may be asking for more trouble.

oh well i'll keep ya'll posted.


ps thanks for everyones help.

[Chuck_Norris]

gery when you put the diaphram back on are you positive it is seated correctly, it sounds like you getting unmetered air somewhere, I know that the diapham can be challenging when it goes back together. just my .02

[gery350]

gery when you put the diaphram back on are you positive it is seated correctly, it sounds like you getting unmetered air somewhere, I know that the diapham can be challenging when it goes back together. just my .02

chuck, that is exactly what i am thinking. the diaphram requires vacuum to overcome the spring tension and rise. there is one channel of metered air that goes to that chamber and it is not clogged. i believe that the plastic carrier that rises is getting jammed on the sleeve at that position or there isnt sufficient vacuum to overcome the spring at full throttle.

ie already done all the test,float level,diff. size everything. and even poured fuel into the diaphram to see if the diaphram might be cracked or have a pinhole somewhere.

i dont know what to do............i think im gonna look for a used carb. and try.

thanks, gery

[Chevy1500z71]

ok, i just hit dynojet.com and it states that on the 03-04 you should have the air mixture screw 3.5 turns out

also yoshis website says that you should be runing a 155 for the 03-04 z400, its an 03 rite

hope that helps some

[Chevy1500z71]

o yea heres the link for the dynojet instructions and its for an 03-04 http://www.dynojet.com/pdf/Q312.pdf

[gery350]

thanks kawyracer. i tell ya its an anomoly(god i hate that word).

i tell ya its not a size issue, its something else.

thanks again.
gery

[Chevy1500z71]

well that kinda sux, just like evry one else said i gess just check ur lines

good luck