jetting/ carb help for my 900

[extreemthrottle]

i have a zl 900 with k&n pods and i believe the baffles have been removed from the stock pipes only because they are alot louder than stock.the carbs i purchased were supposed to be from a 1985 zx900 which i think are the same however these carbs only have one cable hookup.so i got them completely cleaned out, and re jetted closer to the proper jetting i think. i went by the dynojet settings originally but ended up with a 130 main jet, a stock #35 idle jet, and moved the needles to the third notch from the bottom. i put the mixture screws out approx 2 3/4 turns. i bench synced them originally and then hooked up my carb stick to balance properly but could only get close. it does what i would call a "lean pop" consistency at idle then gets worse just off idle. so i'm thinking i'll have to rejet the idle jet now too. i tried to ride it just down the street but she bucks and snarls when i try to take off. i noticed as i moved the needle one notch richer the throttle response was much better but the popping is still there. what do you guys think. when i got the bike it had some crappy pods on it, but it also had 140 mains in it. btw it did'nt run when i got it.

[zlMark]

Follow the CV carb tuning guide in the tech section

[extreemthrottle]

Follow the CV carb tuning guide in the tech section

i actually have been, however i was wondering if anyone new if i was close on my jetting sizes. i know i'm getting close, one thing they say in there is "patience and perseverance" and i'm starting to run low on it...lol

[zl900_moab]

Jets should be fine....130 main and a stock idle jet is what I am running with the SuperTrapps...I had my air screws out about 1 1/4 turns, but that could be the difference from the 'de-baffled' stockers and the Trapps....It sounds right, but the popping and bucking is troublesome...How is the flow from the tank?
moab...

[paulfun]

First thing to consider is the carbs are from a ninja which means they are bigger than the fact zl carbs. So this will mean that useing the recomended jetting for a zl900 will not be an option.

[extreemthrottle]

First thing to consider is the carbs are from a ninja which means they are bigger than the fact zl carbs. So this will mean that useing the recomended jetting for a zl900 will not be an option.

that's what i wasn't sure of.

the flow for fuel is great even with the tank as i'm using a aux fuel bottle (IV bottle as some call it)
the odd things that stand out to me are:

1) that the carbs only have a "pull" cable

2) that the carbs that were on the bike when i bought it are the same.

3) the jetting was the almost the same (new ones had a 90 main jet and the old ones had a 140 main jet)

i knew the 140 was gonna be way rich so i started with a 134 then went to a 130 and its a whole lot better, but the popping and low end is horrendous !!!

just checked and found this also:
ninja 900 had a few different main jets they came with #128 in canada, #130 for racing, also a #132,#135, #140.

the zl came with #120, #122, #125, #128, #130.

[extreemthrottle]

First thing to consider is the carbs are from a ninja which means they are bigger than the fact zl carbs. So this will mean that useing the recomended jetting for a zl900 will not be an option.

upon further investigating i found that the ninja carbs a 34mm and the zl carbs are 32mm. they should still work though, just need to figure out the jetting. was hoping someone here might be able to help.

[zlMark]

Are the 34 mm carbs crammed into the 32mm carb holders?

If you are running pods then a 140 might have been close

[paulfun]

Open the mixture screw to 3 1/8 turns
install the biggest jet you have for the ninja carbs ( Important) from your post it sounds like you have a jet kit in the nija carbs to begin with and the numbers on the jets may not make sense in fact the jet that came in the nija carbs may say 90 but actually be bigger than the 130 you have in. Best bet is to look and measure the opening in the jet and just install the biggest you have.
also moving the needles to the second notch from the bottom

try this and let us know what size jets you end up with and if the problem gets any better or worse that way we have two baselines to go from.

BY the way also important!!!!!!!!
Do not ride the bike if she is running extreemly lean as DAMADGE CAN AND WILL HAPPEN!!!!!!!!!!

[paulfun]

Jets should be fine....130 main and a stock idle jet is what I am running with the SuperTrapps...I had my air screws out about 1 1/4 turns, but that could be the difference from the 'de-baffled' stockers and the Trapps....It sounds right, but the popping and bucking is troublesome...How is the flow from the tank?
moab...

Moab your mixture screw should be out at least 2 1/8 turns with the 900 and stock size carbs. Running the trapps probably a bit more.

[extreemthrottle]

i got the screws turned out approx 4 1/2 to 4 3/4 runs much better now, the popping still there but barely. now the freakin thing just shuts off on me!!! positively electrical. i was moving wires around the fuse box and she shuts off.

i'm guessing i should maybe bump up the idle/low speed jet to a 37/38 but first get the electrical problem under control..

[zlMark]

What did you do with the air suction extreemthrottle? Could be the source of your popping if it hasn't been taken care of correctly.

[extreemthrottle]

What did you do with the air suction extreemthrottle? Could be the source of your popping if it hasn't been taken care of correctly.


NOT SURE I'M FOLLOWING YOU. please explain

[zlMark]

I'll go into more detail later. This really deserves a small tech doc with pics as owners ask about this alot. Meanwhile I gotta go to work,,

Paul can ya chime in here for now??

[paulfun]

what did you do with the emissions when you switched over to the pods?

The big hose that goes directly into the top of the air box and the small hose that goes over to the #4 carb in particular.

[zlMark]

so much for work today :laughing7:

[zl900_moab]

Paulfun....I meant 2 1/4 turns....Typo.
Thanks
moab...

[extreemthrottle]

what did you do with the emissions when you switched over to the pods?

The big hose that goes directly into the top of the air box and the small hose that goes over to the #4 carb in particular.

when i bought the bike, it already had 34mm carbs on it with pods.
there are two tee's that are in between the 1&2 carbs and the 3&4 carbs. i believe those are the only ones i have'nt touched. they are open to atmosphere as i think they are supposed to be.

there is one on each carb that's for the vacuum, three are capped and one for the fuel valve.

my thinking is pointing to either a little larger main jet or a little larger pilot jet. mid range to top end seems very nice and pulls hard, if i stab the throttle at around 3500 to 4000 in first she breaks the tire loose. its really on the bottom that isn't quite right. also i think i'm at the end of the line with the mixture screw because i'm almost 5 turns out. if i go up a size or two on the pilot then the screw won't be out so far and should get me closer....maybe? your thoughts.........:help:

[zlMark]

and what about the airsuction on top of the valve cover? explain what has been done to that?

[paulfun]

"there are two tee's that are in between the 1&2 carbs and the 3&4 carbs. i believe those are the only ones i have'nt touched. they are open to atmosphere as i think they are supposed to be." These are correct but on the front of the carbs the vacume ports inbetween the carb boots and the carbs should be

fromthe #1 carb the vacume port should be capped
the #2 carb should have a line going to the fuel tank petcock
the #3 carb and #4 carb should be capped

the breathers on top of the valve cover should be capped individually or be run into each other then capped.

[extreemthrottle]

and what about the airsuction on top of the valve cover? explain what has been done to that?

they have been capped off. bought it that way, looks like someone used a freeze plug.


"there are two tee's that are in between the 1&2 carbs and the 3&4 carbs. i believe those are the only ones i have'nt touched. they are open to atmosphere as i think they are supposed to be." These are correct but on the front of the carbs the vacume ports inbetween the carb boots and the carbs should be

fromthe #1 carb the vacume port should be capped
the #2 carb should have a line going to the fuel tank petcock
the #3 carb and #4 carb should be capped

the breathers on top of the valve cover should be capped individually or be run into each other then capped.

so whats the difference if its from carb one or carb two?