1978 kz1000a renew and revenge project

There are a lot of guys on here like Zed1015 and "injected" with much more experience that me with these carbs that can probably better advise on the finer points of set up (I do know that "snapping" the throttle open will cause a momentary learn condition as the jets try and catch up with the sudden increase in air speed unless you are using carbs with accelerator pumps)

Maybe they will chime in. 

Im intentionally snapping the throttle to create a worst case. Rolling on throttle still has a minor problem but it’s reasonable. If snapping the throttle is beyond the capability of these carbs then that would be important information and would change the sacrifices I make in solving each problem. I guess an accelerator pump is kind of the perfect solution that they added later. Thank you, very much appreciated.

I read thru this thread and one sentence stood out, "The concept is to have the bike idle at 14.7 for efficiency and enrichen to 12 for power".

Trying to get a air cooled engine to idle at 14.7 is way too lean, and not recommended. There really is no way to accomplish this especially with fixed jetting on +45 year old original equipment.

Snapping the throttle without any extra fuel input (accelerator pump) is just going to create all kinds of lag/lean conditions that are typical of these old round slide carbs. These carbs were always a compromise, they have enough performance for a stock engine, but are not a "high performance" part.

The accelerator pump carbs that Mikuni put out back then were mainly focused on fixing lean emissions jet settings for the USA market. Those pumper carbs helped transitioning between the "circuits", but again they were never intended to be a high performing carb set.

I have found that the newer CVK carbs run "almost" as good as fuel injection on these old air cooled engines. This is the cheapest option without slapping on a set of RS34 flat slides (which work well)

The best way to set up a stock engine combination is with the stock air box, and stock jetting as engineered by Kawasaki. If you want to work with the pipe and even the pods that's fine, but the best way to get it to run correctly is to go back to stock jetting and run air correction jets (for the pod filters)

Great info. Thank you. I’ll quit snapping the throttle. That will certainly make it easier to tune. it’s certainly no problem to set the idle at 12.x.  Chatgpt put some numbers behind your suggestion.
,At idle, going richer from 14.7 → 12.6 AFR will usually lower exhaust-gas temperature (EGT) and combustion/chamber temps a bit—idle load is tiny, so expect a modest drop (think on the order of ~20–80°F / 10–45°Cat the header if everything is burning cleanly).A few idle-specific caveats:

• Too rich → late/slow burn or occasional misfire. That can push some combustion into the header and make downstream EGT read oddly (sometimes higher even though in-cylinder temps are lower). If you see unstable AFR or stumble, you’re too rich.
• Plug fouling & fuel smell. 12.6 at idle is richer than most air-cooled fours need; long idles can soot plugs.
• Sensor behavior. With low exhaust flow at idle, wideband/EGT readings react slowly and can oscillate more.

Practical guidance:

• If your goal is cooler temps and clean idle, a sweet spot is usually ~13.5–14.0 AFR at idle on these VM26SS carbs.
• If you insist on 12.6 at idle, make tiny changes: air-screw IN (richer) in ⅛-turn steps per cylinder, keep idle speed stable, and confirm smooth blips with no hesitation or fuel-smell overload.
• Watch your wideband for stability (±0.2–0.3 AFR ripple) and check plugs after a few heat cycles.

it also said that timing will make a big change in temperature. I’ll test all of the above and provide feedback.

thanks again

FYI - I can do all that without O2 or EGT sensors messing up the exhaust, its called a Colortune plug and its been around for 50 years (before home computers) The easiest way to set the idle circuit adjustment on any carburetor.

I almost went colortune but I’m more comfortable with the Wideband. Lots of years of tuning with a wideband and only a couple with salt deposits, none with colortune. Does the colortune make it possible for you to make a 28 percent jump in afr in 1 step?🤯 

Im not trying to squeeze every inch of power out of this old motor. Just getting it reliable and tinkering. Ive had a 200hp bike. I would just buy another one if I had the need for speed.  The kz1000 is two wheels and a throttle and fun to tinker with but its not something I would want to dominate modern beasts with.

I usually suggest people use the tools they know until they reach their limitations and then find something that feels right. Most people dont have a goal that they worked out before they developed a plan to achieve it. You guys that know these bikes inside and out deserve allot of gratitude for steering people in the right direction, I might get a better set of carbs. Ive used carbs from the late 90’s that are really good like you say. do I have to do any machining to adapt these newer carbs you talked about? 

I heard talk of air correction. Is that on the pilot circuit or does it apply to all 3 circuits? I guess 4 if you count choke.


chatgpt says this;
What to get

1. Carb rack: Keihin CVK32
   Good donors that match KZ spacing:
   • Zephyr 750 (ZR750), Kawasaki ZR-7 / ZR-7S (’99–’05), and ZX600A/B/C (Ninja 600R). These CVK32 racks share the same center-to-center spacing pattern (66-92-66) that works on KZ heads.  kzrider.com
2. Intake boots (head side)
   • Use the matching offset boots for the CVK32 donor family (ZR750/ZR-7 boots are interchangeable and made for that rack’s spacing/angle). The 550 vs 750 boots differ—stick with the ZR750/ZR-7 style for CVK32.  kzrider.com
3. Throttle cables & choke/enricher cable
   • Easiest path: use throttle + choke cables from the CVK32 donor (ZR-7/ZR750), or have Motion Pro make a set to match your KZ controls to the CVK bracket geometry. (CVKs use a push/pull throttle and cable-operated enricher.)
4. Air filters (pods) or airbox hookup
   • Pod size depends on the CVK32 bellmouth OD (varies slightly by rack). Many CVK32 setups use ~54–55 mm ID pods, but measure your rack’s filter spigots with calipers and buy pods to the actual OD. (Examples and discussion around pod sizing exist, but measuring is the only reliable way.)  Amazon+1
5. Fuel plumbing
   • Single 5/16 in (8 mm) ID fuel line with a low-restriction tee, or the OEM ZR-7/ZR750 fuel rail if included.
   • If you run a vacuum petcock, be sure the rack has at least one vacuum barb to operate it; otherwise plan for a manual high-flow petcock (Pingel-type) and cap any unused vacuum ports.
6. Vacuum ports/caps & sync fittings
   • Ensure each intake runner has a vacuum nipple (or use the CVK’s own sync takeoffs) for syncing. Buy quality rubber caps for the unused ones.

Baseline jetting to start (pods + 4-into-1, 1000cc)

• Stock ZR-7S CVK32 jetting is roughly Main #108 / Pilot #35 (Keihin sizes). On a 1000cc engine with pods/pipe you’ll be richer than stock: start higher than 108 mains and plan to tune with your wideband.  Scribd+2riderforums.com+2
• Practical starting range (to be verified with AFR pulls): Main ~120–130 (Keihin), Pilot ~38–40, needles raised 1 clip from stock. Then iterate. (Pods typically need up on both main and pilot vs. stock donor settings, as noted by tuners.)  Reddit

Install/tuning tips

• Check slide diaphragms for pinholes and the CVK slide vents for obstructions.
• Sync mechanically, then fine-sync with vacuum gauges.
• Set fuel level by clear-tube on each bowl.
• Use your wideband targets (you’ve been using 12.6); expect to end up with mains significantly larger than donor #108 on a liter-bike.

If you want, tell me which donor rack you’re buying (ZR-7, Zephyr 750, etc.). I’ll spec the exact boot part numbers, typical pod ID for that rack’s bellmouth, and a first-pass jet set so your first test ride lands close.

bry195 wrote:

I heard talk of air correction. Is that on the pilot circuit or does it apply to all 3 circuits? I guess 4 if you count choke.


 

Air corrector jets are used when removing the stock airbox and running open carbs, stacks or pods.
They only apply to the main air jet circuit that bleeds air to the needle jet tube.
They correct the momentary lean condition that occurs on the transition from the pilot jet to the needle jet which causes off idle bogging and hesitation around 2 to 3k rpm and are a more refined and targeted alternative to the practice of fitting bigger pilots and lifting the jet needle which only masks the issue whilst richening the entire fueling curve that can cut top end power by up to 25%..

That sounds like exactly what I need!

I tried to follow the link in your signature but it didnt work. How do I get these jets?

bry195 wrote:

That sounds like exactly what I need!

I tried to follow the link in your signature but it didnt work. How do I get these jets?

Email me at    zed.1015@yahoo.co.uk    and i'll supply all the info etc.
Thanks, Rob.

Just read back through this thread and few things to note. 

1. DO NOT use cheap Ebay, Amazon, etc carb kits and jets as they are wildly inaccurate and do not flow like for like with OEM or even each other from the same kits.
If you have these fitted then throw them in the bin..
Only ever use Genuine Mikuni or Japanese Keyster parts.

2. No amount of "Rubber rejuvenator" will reliably cure worn choke plunger seals so get them repaired with NEW seals or source new plungers otherwise you will always get inconsistent A/F readings and rich running.

3. Each carb requires the same jetting and needle position which on your stock motor with pods means the stock pilot , needle in middle groove, 107.5 main and air correctors.
 Readings on cylinders that are wildly adrift from their neighbours will be due to other issues such as worn needles, needle jet or even individual cylinder differences which should be addressed directly and not compensated for with mismatched jets etc..

4.  I will also say you are going down an endless rabbit hole with the A/F meter chasing perfection you will never achieve and trying to even out carb to carb discrepancies which show up on a screen that you will never feel in real life riding conditions.
Whilst these VM carbs are some of the best ever produced their adjustments by their very nature as stock are limited by the individual fuel circuits being controlled by fixed jetting which doesn't seamlessly flow from one stage to the other ( hence the need for the air correction mod when removing the airbox ) .
You are never going to get the perfect or near perfect stepless fueling slope that that can be achieved with advanced fuel injection methods but once set up within reason you would never know.



 

To back-up Zed's comments. I too do a lot of stuff pertaining to the carb "scene", it's all i know. Pay Heed to his comments. Lots of person's immediately turn to their specific Brand of motorbike and go exclusively to that website. All the Manufactures NEVER made carbs, outsourced so go directly to the Maker. A sampling shown, everything is available as original just have to know where to look up the original type and correct part numbers. I too have been using the Colortune as well for well over a decade. It has it's perimeters of function but you can check each cylinder individually where as what you're doing, singular bung for reading, can't pinpoint which one is out of wh  ack.      

asphalt900 wrote:

To back-up Zed's comments. I too do a lot of stuff pertaining to the carb "scene", it's all i know. Pay Heed to his comments. Lots of person's immediately turn to their specific Brand of motorbike and go exclusively to that website. All the Manufactures NEVER made carbs, outsourced so go directly to the Maker. A sampling shown, everything is available as original just have to know where to look up the original type and correct part numbers. I too have been using the Colortune as well for well over a decade. It has it's perimeters of function but you can check each cylinder individually where as what you're doing, singular bung for reading, can't pinpoint which one is out of wh  

Clay this guy has put "bungs" in all 4 headers so he is measuring "individually" - I think the biggest "rabbit hole" was him trying to get carbs to act in the same way as fully "managed" EFI system (which would drive a Tibetan monk to distraction )