Kawasaki Ninja ZX-6R Forum banner

[sorted] ZX6R F series not ok between 4-7k rpm but good between 1-4k and 7k to redline

848 Views 52 Replies 5 Participants Last post by  Brandon35
Hello everyone,

I have an F series ZX6R and I am unable to figure out what is wrong... Can someone help me? 馃槵

Here is the situation:
Idles normally.
I can readline the bike in neutral and I do not have any weird behaviour.
I can readline the bike in 1st gear OK and in 2st gear with a slight moment of hesitation at 5k rpm and will reach 7k and goes to the red line perfect.
Then I can pass 5 6 7 k at third gear albeit with a lot of misfires and cutoffs and then off I go to red line.
On fourth gear and above I can't pass 5k it will misfire too much and throw me forward and backwards.
Last thing: when I go to red line say in third gear but decelerate (whilst leaving the throttle 20% open) (staying in 3rd gear) and enter the zone 7-6-5-4k it seems to accentuate the issue the engine start to burble, bog down, sort of misfire or was starving for fuel.

Things I've done:
I've cleaned the carbs
New sparks
New ignition coils.

Things I have not done:
Compression
Valve clearance
Check the rest of electrical system

Because of the weirdness at 5k my suspicions went to the transition from pilot jet to needle jet and the diaphragms. I've checked again and again if not pinched or whatever but everything is installed ok...

Any help is appreciated 馃憤 please.

Thank you!!!!
See less See more
21 - 40 of 53 Posts
I ran out of any forgiveness about 5000 idiotic stupid posts ago (from all the idiots).
It's okay, most of us know by now that your "you fucking morons!!!!" type phrases really translates to "common guys, you can do better" in normal person speak 馃槀
  • Like
Reactions: 1
I'll do a test run tomorrow and keep everyone posted ;-)
Funny enough, I'm about to take my carb off and clean it out due to another batch of bad california fuel. I'll show you my exact routing when I get pictures.

With bad gas and ethenol, definitely keep some fuel stabilizer handy for longer periods of not riding.
Best to keep a full gas can in the garage with stabilizer in it. Then top up the tank when you get home.
  • Like
Reactions: 1
It is not semantics though.

It is incorrect information being doled out to the masses (most are dumb) and then they run with that incorrect information.......

I am just here doing my part to increase the intelligence of the masses and nip the dumb fucking shit in the bud!

easy solution to the last part...... don't be a moron!?! I know simply concept, too bad reality is, society has been filled and bred by so many morons it is impossible to rid them all now- they are the biggest breeding population just producing more and more morons
Well yea. obviously

I was being sarcastic. I may not be the smartest guy in the room. But I know the difference between suck and blow lol.
It is not semantics though.

It is incorrect information being doled out to the masses (most are dumb) and then they run with that incorrect information.......

I am just here doing my part to increase the intelligence of the masses and nip the dumb fucking shit in the bud!

easy solution to the last part...... don't be a moron!?! I know simply concept, too bad reality is, society has been filled and bred by so many morons it is impossible to rid them all now- they are the biggest breeding population just producing more and more morons
Ever seen the movie idiocracy ? It was funny when it was released. Now it鈥檚 basically a reality show
  • Like
Reactions: 1
6
Alright here are the pictures.

Pic 1 and 2) my smog block-off plates and what it would look like if you were to connect the original hoses together instead of buying the block-off plates

Pic 3) my float bowl to upper airbox hose configuration. Could be done in a cleaner way but meh

Pic 4) what it looks like with everything assembled.

Pic 5) my carb boots reversed, showing all the vacuum lines to the boots capped (with both the airbox and smog mod, none of these lines are used)

Pic 6) capped air tube fitting on the throttle side of the airbox

Attachments

See less See more
  • Like
Reactions: 1
2
Thank you so much so I've followed your instructions and now the bike worked perfect on the previous issues, no more hesitation where there was.

BUT 馃槀馃槀

I tried the bike had in temp and did 15 min run.

I did red line it a couple of time (whilst driving) and noticed a new and different slight hesitation and stumbling (on acceleration and on charge at exactly 9k rpm, whatever the speed or gear 1 2 3. But would go through it and then fly to red line like very good!

But no issue when decelerating and passing the 9k rpm mark.

Sparking clean on the rest of the rpm band.

Attachments

See less See more
It's an issue I did not have before and I did add a new air filter and I heavily soaked it into oil so maybe I should try without air filter ...
Your air filter is likely far too saturated, not convinced that's the cause of your remaining issue, but it's almost certainly in the right area. Even one worn out (hard, brittle, cracked or leaking) vacuum line would cause issues.

Before Lloyd can jump in, there's no such thing as a clean enough carb......
  • Like
Reactions: 2
^ Agreed on clean enough carb. I cleaned mine out about 4 weeks ago, and check out what mine looked like yesterday...

Carb cleaner in ALL passages (pilot, main, idle, and float needle), clean out ALL jets, and use compressed air in all passages to clear them.

Settings per the manual:
#1 and #4 main jets: 145
#2 and #3 main jets: 150
Pilot jets: 35
Idle mixture screw: 2 turns out

My settings for reference only:
#1 and #4 main jets: 155 *(will reduce to 150 soon)
#2 and #3 main jets: 160 *(will reduce to 155 soon)
Pilot jets: 35
Idle mixture screw: 2 and 1/8 turns out

My main jets are too rich, I just keep forgetting to order 150 jets.

Again, make sure ALL your vacuum/pressure lines are serviceable and fit snug.

Attachments

See less See more
Wait you are telling me the jets from the cylinders in the center are bigger than the outside ones?

Ok I actually never paid attention to this and did not know.

Is the size written on them? Is it 145 and 150 what? Microns?
Yea. On multi carb setups the carbs are never carbon copy鈥檚 of each other. They need to be setup as such then synch tuned as a unit
Wait you are telling me the jets from the cylinders in the center are bigger than the outside ones?

Ok I actually never paid attention to this and did not know.

Is the size written on them? Is it 145 and 150 what? Microns?
Correct, center main jets are bigger. I believe that has to do with how hot the engine gets towards the center two cylinders and what that means for fueling (aka, more fuel in with richer burn means a cooler burn which helps level out how hot the center gets, and even out the center from the outside). Leaner burn = hotter burn (another "ask me how I know" scenario).

Each main and pilot jet will have a size stamped on it. Sometimes they can be hard to read.
You'd also be wildly surprised at how different the bike will sound/feel/respond once the carbs are synced. Highly highly highly recommend doing this.


For this engine, you always sync #1 with #2, then #3 with #4, then you can work the sync screw between #2 and #3 to sync both sides to each-other. You can do this yourself pretty easily, but recommend you buy a QUALITY
gauge set. Garbage in = garbage out.
Oh my gosh 馃椏馃椏 what a pain in the .....

I had bikes with two cylinders only so two carbs in the past so I could manage but now 4 -_-

Okay I just read the book and you are correct! (Not that I thought you weren't) I'm going to tear this apart and have a look .. again... 馃く馃く馃く

Question what are the main air jet, pilot air jet and strater jet? Dismantling the carbs I only came across the main jet, main jet holder, pilot jet and pilot screw that I could remove.

Attachments

See less See more
Well yea. obviously

I was being sarcastic. I may not be the smartest guy in the room. But I know the difference between suck and blow lol.
I am sure your boyfriend appreciates that knowledge too............
  • Haha
  • Like
Reactions: 3
Oh my gosh 馃椏馃椏 what a pain in the .....

I had bikes with two cylinders only so two carbs in the past so I could manage but now 4 -_-

Okay I just read the book and you are correct! (Not that I thought you weren't) I'm going to tear this apart and have a look .. again... 馃く馃く馃く

Question what are the main air jet, pilot air jet and strater jet? Dismantling the carbs I only came across the main jet, main jet holder, pilot jet and pilot screw that I could remove.
Sometimes the fuel and air holes for the start/idle circuits are called "jets" even though they are pre-drilled holes and don't have any removable parts. Those are just circuits within each carb that cannot be changed.

To hit on this one more time, my above jet settings (not the factory setting but the ones I have) are NOT something you should aim for. To quote Lloyd from a long time ago, these engines are sent out from the factory with larger than necessary main jets already. If yours are stock, keep it that way.

I'm personally ok with a size or two bigger on my jets because I don't intend to dyno the bike any time soon and want to remain on the rich side rather than anywhere near lean. This is probably killing my fuel economy but it makes me feel "safe". I have a K&N high flow filter, block-off plates and aftermarket slip on; stock jetting is still fine for this setup.
Oh my gosh 馃椏馃椏 what a pain in the .....

I had bikes with two cylinders only so two carbs in the past so I could manage but now 4 -_-

Okay I just read the book and you are correct! (Not that I thought you weren't) I'm going to tear this apart and have a look .. again... 馃く馃く馃く

Question what are the main air jet, pilot air jet and strater jet? Dismantling the carbs I only came across the main jet, main jet holder, pilot jet and pilot screw that I could remove.
The air jets (main and pilot) are both in the inlet side of carb

When you removed the airbox, you would have seen them at the bottom portion of the inlet to the carbs

sorry I don't have time to find a picture
Here you go; not the exact same carb of course but you get the idea. Starter jet is the pressed brass fitting inside the float bowl next to the main jet, and the main/pilot air jets are the drilled holes in the throat of the inlet (between the throttle valve and the throat of the airbox).

No need to remove the brass starter jet, and no adjustments can be made to the physical main/pilot air jet (that I recall) outside of the idle-mixture screw adjustment.

Attachments

See less See more
I am sure your boyfriend appreciates that knowledge too............
He identifies as a her. It鈥檚 MA鈥滱M! ITS MA鈥滱M
  • Sad
Reactions: 1
21 - 40 of 53 Posts
Top