CARBY GURU NEEDED or someone with half an idea.

[damo1]

Hi all,

I need some advice on my Gpz9.

I have pulled the air box and am running single carb uni filter's and a 4-1 as well as a Dyno jet kit.

The dyno jet kit stated running the clip on the needle at notch 3 ( in the middle) and run the pilot at 4 turns out.

This was running way to rich and it would back fire and burble off idle until about 3 grand then clear (it was like a light switch) and ride fine but would run out of puff in the top end.

So I dropped (down the needle to raise the needle) the needle clip one notch to richen the mid to top end, this worked a treat and the thing id now a rocket ship through the middle and up top.

I also wound in the mixer screw to about 2.3/4 turns out it runs better off and has a stumble at around 2.5grand but not that bigger deal cause I very rarely travel at those revs.

Now the last couple of days when riding in traffic the bike seems to foul the plugs at idle or just off and only a good rev will clear this.

So my question is this , im pretty sure that it's the idle jet/ mixture screw that's the problem with my limited knowledge??

So am I safe to continue to turn the mixture screw in another 1/2 turn with the uni filter and not risk leaning out the bottom end to much or should I be looking else where??

Im pretty sure that standard was 2 turns out - with the air box and standard exhaust, so im heading back to a factory setting. To me its gonna be to lean with the mods?

Yes I know a dyno would fix it or give me an idea, but remember before dynos people could work this stuff out
just after some direction on the above problem , im happy wasting my weekends with the carbs on a bench.

cheers damo

[Hillsy]

Give it a go Damo - sometimes carbs go richer in areas where you'd logically think they would lean out (like with pods and a 4-1).

The rule of thumb is to set the idle circuit screws so the idle is at it's highest without stumbling or popping, then back down the idle screw to suit. A carb balance will help things down low in the idle circuit, too.

BTW - that's a yes to your question - the idle curcuit needs adjusting.

[evad]

Hey Damo, maybe using a wide band 02 set up would help to pin point the problem?

[damo1]

Hillsy:Cheers mate ,will do.


Evad: a what?? I don't know what the fuck that is mate??

[oldskool]

Air screw at 1.5 - 2 turns clip in the middle smaller of the 2 main jets supplied.
It was a stage 3 Dyna jet kit hey?

[evad]

Its a sensor that goes in the exhaust, mounted into a weld on bung, this is one by innovate

http://www.innovatemotorsports.com/products/MTXL.php

I have found this thread by a guy on the KZ riders forum that runs through what it is and how he has tuned his bikes carburation with it.

http://www.kzrider.com/forum/3-carburetor/307483-installing-wideband-o2-sensor#307634

And a second thread

http://www.kzrider.com/forum/4-electrical/483702-does-anyone-run-an-airfuel-ratio-gauge#483747


Oldskool seems to have a handle on it though. Hope you get her running right.
Interesting thing from this is just how good carbs are when they are working correvtly, I always thought that they would be good at some rpm and load areas and not in others. Lous results were a bit of an eye opener!!

[damo1]

Air screw at 1.5 - 2 turns clip in the middle smaller of the 2 main jets supplied.
It was a stage 3 Dyna jet kit hey?

Na its called a stage 1 , that's the only one you can get apparently from dyno jet.

1.5 to 2 turns?? it says 4 turns out in the instructions??

I ran the bigger of the mains because the other smaller jets were for the standard airbox /filter + exhaust.

[damo1]

Its a sensor that goes in the exhaust, mounted into a weld on bung, this is one by innovate

http://www.innovatemotorsports.com/products/MTXL.php

I have found this thread by a guy on the KZ riders forum that runs through what it is and how he has tuned his bikes carburation with it.

http://www.kzrider.com/forum/3-carburetor/307483-installing-wideband-o2-sensor#307634

And a second thread

http://www.kzrider.com/forum/4-electrical/483702-does-anyone-run-an-airfuel-ratio-gauge#483747


Oldskool seems to have a handle on it though. Hope you get her running right.
Interesting thing from this is just how good carbs are when they are working correvtly, I always thought that they would be good at some rpm and load areas and not in others. Lous results were a bit of an eye opener!!

Mate that's to high tech for my simple brain, but I appreciate the links

cheers

[Redmohawk]

Na its called a stage 1 , that's the only one you can get apparently from dyno jet.

1.5 to 2 turns?? it says 4 turns out in the instructions??

I ran the bigger of the mains because the other smaller jets were for the standard airbox /filter + exhaust.

The settings on the box are an aproximate , unless you run exactly the same filter/box/pods/pipes as they have on they're setup it will be out also altitude of bike Ie sea level as opposed to 1000 feet above will make a difference.

If its running that rich at idle its fouling plugs at idle changing the mixture screw half a turn is prob the best bet (and not going to burn the motor) , the 2500 rpm stumble MAY clear up with a leaner Idle mix.

[Cruisecontrol]

Advice?

This is a streetfighter forum!
Get rid of the plastic or fuck off!!!

Edit
Damn deleted posts makes that a tad irrelevant now...

[BANDITROD]

I know what you're talking about dan lol

[damo1]

Advice?

This is a streetfighter forum!
Get rid of the plastic or fuck off!!!

Edit
Damn deleted posts makes that a tad irrelevant now...

hahaha yes I notice the deleted post this morning.

This place going soft or what? you cant even ask people to leave anymore.

[damo1]

Ok back to the topic,

The bike seems to run better with the leaner tune but now has a different problem.

After pulling up and the lights the bike settles into a nice idle at around 1200rpm.

After idling for about a 1 min in traffic it then drops down to about 500-650rpm on its own.

Its not like a lean mixture when the idle hangs then drops off, its a prefect idle and them after a bout a full min it just drops suddenly to the lower revs.

I have tried winding up the idle when it drops and it will idle fine then at the next set of lights the idle is up near 2k.

I then reset it at around 1200 again and it idles fine then after a time idleing in traffic it does it again.

No the throttle cable is not sticking and this is a new symptom after the mixture adjustment only.

Any ideas have I gone to lean??

[latheboy]

Does it sound like it's sneezing when at idle?
If it's too lean it will.

Are the butterflies sticking?
Doesn't matter how good the cable is if the slides/butterflies are sticking.

Does it have slides? Might have a hole in one of the diaphragms.

[damo1]

Does it sound like it's sneezing when at idle?
If it's too lean it will.

Are the butterflies sticking?
Doesn't matter how good the cable is if the slides/butterflies are sticking.

Does it have slides? Might have a hole in one of the diaphragms.

I don't think so ill listen for it this arvo.

No the butterflies are not sticking.

Yes it has slides and no the diaphragms are fine.

[oldskool]

You need a stage 3 for airbox removal the needles and springs need changing.

[damo1]

You need a stage 3 for airbox removal the needles and springs need changing.

I called the guy that supply's the dyno jet kits and explained my mods - he told me the only kit they make for these now are for yrs86-92 and is a stage one there is no other kits available for a gpz??

Is there a different kit that I can get other than the stage 1?? any ideas where?

[damo1]

I have changed the springs and drilled the slides with the drill bit that came in the kit.

Are they the springs your talking about or are there different springs again for stage 3 kits?

[damo1]

Maybe I need to clarify this.

I changed the main jets to 137s (DJ) and adjustable needles.

I also replaced the springs and drilled the slides.

All the above was listed as to do's in the kit and came in the dyno jet kit I brought.

Dose that change anything?

[oldskool]

http://www.dynojet.com/jetkits/motorcycle/kawasaki.aspx

[Hillsy]

http://www.dynojet.com/jetkits/motorcycle/kawasaki.aspx

According to that, the only difference between the stage 1 and 3 is the size of the main jet used. Both get the slides drilled and use the DJ springs.

Also, it says to have the idle mixture screws backed out 4 turns (I'm looking at the 84-86 ZX900).

EDIT - just re-read your first post Damo and I see you started at 4 turns out and it was shit. I think you'll just have to play around with it and get it the best you can - might be a case of it never running perfectly everywhere without the airbox.

[Redmohawk]

Without running it over a dyno or at the least a wide band sensor on the road your stabbing in the dark unless you've done a fair amount of tuning by feel yourself. And tuning via the net with a bunch of gibbons like us at the other end is a great way to spend heaps more time on the same job,.

I'd hunt down someone in your area with some hands on experiance at tuning a bike or get your hands on a wide band sensor ($200) will get you one from the states with a bung and gauge . Once the bike is tuned you can plug the bung and use it on the next bike you mess with (thats what I did)

[evad]

I have read that the A7 and A8 run much leaner and have lower power outputs thank the a1 to A6 models, apparently the difference is in the carbs airbox and exhaust. I see that FActory pro have 2 different kits for the gpz9 but they are listed as A1 to A6
Maybe email Craig at gpzzone.co.uk and ask him what the normally do to sort them out?

[oldskool]

Now there is some good advice!
Other good advice would be buy a GSXR.

[damo1]

Thanks all for your feedback.

The later models had smaller mains and different needles to meet emissions laws and lean them out that's why they only had 100hp.

The earlier ones had 115hp.

The carbs are exactly the same as the earlier ones, I have pulled the air boxes out of my early 86mod and this 92 and the airboxes are the same also.

cheers

[damo1]

Ok bit of an update.

I was gonna change the needle again on the weekend and found one of the carb bodies had broken ?? not 100% sure what the fuck happened here??

Any way I pulled the carbs out of my spare bike and just pure laziness may have sorted the tune.

I changed the mixture screws back to 2 full turns out and changed the slides/needles and springs from the dyno jet kit into the spared carbs.

I checked the mains in the pares and they are 137.5, so I knew the dyno jets were 115 ( yes I know that the numbers are different between d/j and kienin)

But I thought i'd try the 137.5 and see how it would go.

It took ages to fire up for some reason, but settled into a prefect idle once fired.

It rev'd clean right off idle with no hesitations at all.

It rides better than before and rev's clean and idle's prefect for long periods of time with no drop off as before.

I know someone mentioned different carbs from early to late previously but I just thought it was the mains and needles??

Maybe these carbs are different somewhere? or maybe the different mains are the fix? I dunno what I have done but I fixed it and fixed it good -??

Anyone shed ant light on the mains flows and differences?? would be interested to know the difference if any?

Cheers damo