Carburator question

[Baggey22]

I have a 2008 Kawasaki ZZR600 with 6,050 miles. It's mostly stock except for a Yoshi slip on.
It's having this habit of a wandering idle when it's warmed up. When I'm sitting at a stop sign or stop light the idle will raise to around 3000RPM and stay there. Also if I rev the engine it doesn't immediately drop back to idle like it should, it slowly goes back down the rev range until it gets to idle. Trouble is it revs fine throughout the range while riding.
I've had two ideas for the problem. One person said the jetting is off because of the slip on exhaust can (running too lean on stock jets), the other suggestion was something to do with the butterfly valves sticking.

Anyone here have different suggestions/ideas? Thanks

[Degsy]

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Donny says vacuum.

[Sheppo]

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Donny says vacuum.

The butterfly's or slides could be sticking as well.

[Baggey22]

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Donny says vacuum.

Vacuum...... How do I check for a vacuum leak?

The butterfly's or slides could be sticking as well.

How can I remidy that?

[Doc]

Vacuum...... How do I check for a vacuum leak?



How can I remidy that?

Stop by the house with it this week.

[Degsy]

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Docs gonna teach them to suck properly.

[Doc]

Lots of wd40 and a screwdriver.

[Baggey22]

Stop by the house with it this week.

When is you free??

[MellowYellow]

Baggey 1st check the A/F mixture screws. Just had the same problem on my Gixxer. 3 carbs were 3 & 1/2 turns out the 4th was 2& 1/2. Set them at 2 turns out and no more 3K idle when warm.

[Baggey22]

Yea, that's also something to note. It'll only wander when the bike has been warmed up.

[markbvt]

It's too lean. Bikes are jetted lean from the factory due to emissions regs. Introducing any changes to the intake/exhaust system to increase flow makes it even leaner (as has been done to yours with the slip-on pipe).

Happen to know if the previous owner made any carb adjustments at all? Pilot screw adjustments, anything?

--mark

[MellowYellow]

Yea, that's also something to note. It'll only wander when the bike has been warmed up.

Mine only did it when warm also. 160 +

[vintage ex race]

bike is running lean you will need to fatten it up a bit

[Baggey22]

I am unaware of any adjustments by the previous owner.

[Doc]

I am free all day. Unemployed.

[markbvt]

I am unaware of any adjustments by the previous owner.

There probably weren't any... and as a result your bike's running too lean.

We can make a partial change by adjusting the pilot screws and shimming the needles to richen up the midrange a bit. But that won't help at full throttle.

Want to plan some time this weekend to look at it?

--mark

[scottieducati]

It's "carburetor"... Which could be your problem to begin with

[gamorg02]

doesn't opening an exhaust make a system go richer?

my first thought was sticking slides

[ChicknStripEatr]

Baggy, before you go tearing your bike apart, check the choke cable. On my older model ZX-6R (same as your ZZR) the choke cable would occasionally seem as though it would hang up causing the idle to rev slightly. There is an adjuster on the cable, try backing that off 1st.

2nd, for the bike down revving (this is going to sound dumb) does your throttle grip rub ever so slightly against the bar end? I had to shave the stocker grip slightly with a razor blade.

[markbvt]

doesn't opening an exhaust make a system go richer?

No. Leaner.

--mark

[gamorg02]

No. Leaner.

--mark

i found running smaller mains on my vmax when i had a slip-on helped more, and the more restrictive mufflers (cobra) needed larger jets. is the v-max different or do I have it backwards.

obv opening up the intake leans it out yea?

[obsolete]

i found running smaller mains on my vmax when i had a slip-on helped more, and the more restrictive mufflers (cobra) needed larger jets. is the v-max different or do I have it backwards.

obv opening up the intake leans it out yea?

The less restrictive you make an engine (intake/exhaust) the more O2 is introduced into the combustion chamber. If the fuel metering is at a fixed amount then you have more O2 and the same amount of fuel and therefore a leaner condition than before.

[Baggey22]

I'm gonna go for a ride and then pull a plug (or 4) and see what the plugs will tell me.

Baggy, before you go tearing your bike apart, check the choke cable. On my older model ZX-6R (same as your ZZR) the choke cable would occasionally seem as though it would hang up causing the idle to rev slightly. There is an adjuster on the cable, try backing that off 1st.

2nd, for the bike down revving (this is going to sound dumb) does your throttle grip rub ever so slightly against the bar end? I had to shave the stocker grip slightly with a razor blade.

I'll check the choke and bar end while I'm there.

[Baggey22]

UPDATE!: So I went over to Doc's last night and put new jets into the ZZR as well as a new K&N air filter. I only rode home from Doc's but so far the bike is running MUCH better. There's a little more midrange and high end response. I did get it up on the highway once we were done and checked smoothness throughout the entire rev range and it seems to be great! I'll know more once I ride it more.

[Doc]

Glad I could be of service.

I would have liked to tighten the carb boots up some but other than that everything looked good under there. Carbs were clean, no sticking slides etc.