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Carburetor synchronization/synchronisation - 45 minute Do-It-Yourself

42K views 47 replies 20 participants last post by  e1_ZX-9r 
#1 · (Edited)
This should be relevant to carbureted engines with 2, 3 or 4 cylinders. EFI throttle body bikes, review your repair manual's procedure. For 2005-2006 ZX6 TB sync CLICK HERE. A highly recommended Do-It-Yourself, especially if you can borrow someone else's sync tool. It is really that easy.

My used ZX-9r ran poorly at purchase and I performed an eyeball sync* myself last year to smooth most of it out, but it still wasn't perfect. I decided to perform a real carb synchronization and purchased a Carbtune Pro 4 (58 GBP/$85 shipped) after reading good reviews.

Following my Haynes repair manual, I warmed the bike up (140 degrees) raising idle to 1,500 RPM, turned it off, removed the gas tank, connected the sync vacuum tubes to their intake points (below each intake boot), started the bike, sync'ed cylinders 1&2, then 3&4, then left side to right side. That took a whole 2 minutes, so for good measure I fueled the carbs up one more time, blipped the throttle to 1,800 to reseat the butterflies and repeated. The Carbtune made this work out to be child's play.**

No more ruppity-ruppidity. She purrs like a new bike, holding right at 1,100 RPM. Throttle body synchronization theory says that the engine will start easier, run cooler, be more efficient, smoother, with better throttle response & power. :crazyloco

04/2009 1,000 mile update I had to sync her again after some 1/4 mile runs for a Youtube short vid. Dunno why. The science holds true. She runs cool & smooth, starts easy & is a joy to ride. She's very miserly for something so wickedly powerful.
I only wish I would have done this 6 months ago.

*The science behind cylinder vacuum efficiency depends on many factors other than carb/EFI butterfly position; pilot air screw symmetry, pilot circuit clogs/efficiency, minor discrepancies in piston and ring fit, valve opening gap, valve air flow efficiency, carbon build up, temperature, oil weight, etc. Therefore, the only way to accurately synchronize the draw evenly is to use a tool that can measure each cylinder's efficiency.

** Before syncing carbs, always set the pilot air screws symmetrically. If you suspect the pilot air circuit may be dirty, pull the screws, clean the circuit plumbing, set them symmetrically, then perform your sync.
 
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#5 · (Edited)
A visual to help

I get asked occasionally on how high each bar should be, to which I answer it doesn't matter.

Assume this look at the sync tool, where the '*' symbolize the vertical bars:

..........*
.......* * *
0) * * * * sorry about all the periods, it's the only way to line things up.

.........*
...* * * *
1)* * * * sync # 1 & 2 with the screw between them

.........* *
...* * * *
2)* * * * sync # 3 & 4

...* * * *
3)* * * * sync left side (1&2) to right (3&4)

Or pictorially --
When connected to a vacuum sync tool the discrepancies become all too apparent.

before


after



A word of recommended caution. For best results, get your carbs set the way you want first. In other words, set the idle mixture screws identically and set float heights first. Then sync your carbs. Done right, your ride should be dreamy. (See picture below showing the three synchronization screws).

 
#32 ·
By base carb, meaning it is hooked directly to the throttle cables, and all the other carbs adjust to it. In this case Yes. At least for the 11, but I'm pretty sure most banks are that way. This doesn't really make it a "master" but to change the idle positon of 2 you can only adjust the idle screw, none of the sync screws will change #2. This is why you do 1 to 2, 4 to 3 (notice when you adjust the right most screw, 4 moves, not 3) and then 3 to 2 or right pair to left pair.

But good reading and with the amount of real time that we spend in the low throttle opening range on our bikes it is essential for good operation.
 
#9 ·
Always consult your repair manual for the exact procedure and tune your jetting prior to the synchronization, but chances are your four cylinder ZX-11 has the standard three balancing screws as shown <here>. And therefore the answer is no. There is no carb that is the master to which all others need to comply.
 
#13 ·
Also look for the clear plastic restriction tube pictured below. Without it you'll have no way to get a steady reading...perhaps why this guy is selling it...'hey man, it doesn't work right....' ...No kidding. :angry Ever try reading the assembly instructions. :headscratch

The tube is cut into four equal ~1" lengths and inserted into each black vacuum tube, so it goes black tube, clear, black tube.
 
#17 ·
:headscratch The Carbtune vacuum hoses are attached, in order, to their respective intake vacuum nipples (#92150). You remove/pop-off the existing vacuum hose, attach the Carbtune hose, sync the carbs, then reattach the existing vacuum hose to its exact intake vacuum nipple.

Picture compliments of CyclePartsNation.com

 
#38 · (Edited)
I found this thread in search, and thought, FINALLY. e1 has a zx9, I'll be able to figure out where to connect these damn hoses. Get down to this post...Oh yes, finally here it is...NO PICTURE.:banghead :banghead :banghead


Between this thread, my haynes manual, and the cycleparts break down of the 03 zx9r carbs, I still can't seem to figure out. e1, turn on your flashlight and shed some light for me please....They are CVK just for reference

Here's a new link for 03 carb parts breakdown
http://www.cyclepartsnation.com/oemparts/a/kaw/500b273cf8700223e479182e/carburetor
 
#19 ·
Oh yeah, sorry. I just assumed you had a 9. Different models will have different configurations. I know another rider had to order the 4th nipple just so he could do his. What bike do you have? I could look it up on CyclePartsNation to see your configuration.

Yup. ZX-9r is pictured above.
 
#22 ·
Not to worry. It's okay to take the box off if that's required for your model. By the sound of it, your ZX-11's sync screws face up at the front of your carbs. On my 2000 ZX-9r they are at the front but face backwards. On my second ZX-9r they face up and the airbox has to come off.

If I find a way to adjust them without taking the airbox off, I'll post it up. I think the airbox-on method results are more reliable, b/c my second bike is already out of sync after only 1,000 miles. Owning a tool like the CarbTune is the only way to go.
 
#23 · (Edited)
How 'bout that!

EDIT: The quoted material may have been the result of a plugged pilot jet. I'm leaving it for historic relevance, but I am once again syncing at 1,500 RPM.

Learned something new after an extensive sync session on one of my bikes. Best results on my newer bike (using CVKD-40mm carbs) came from synchronizing the TBs at 900 RPM, not 1,500 as I've done in the past (on CVRD-40mm carbs).

And interestingly enough, the sync pointed out that my float heights are too low (lean) on this bike. F*CK. I just love this tool!! :rofl
 
#24 ·
Learned something new after an extensive sync session on one of my bikes. Best results on my newer bike (using CVKD-40mm carbs) came from synchronizing the TBs at 900 RPM, not 1,500 as I've done in the past (on CVRD-40mm carbs).

And interestingly enough, the sync pointed out that my float heights are too low (lean) on this bike. F*CK. I just love this tool!! :rofl
As many carb questions pop up...this should be stickied IMO. :crazyloco
 
#26 ·
There's a difference between 'within specs' and how the height affects the low speed fuel circuit's lean/ideal/rich fuel delivery:

"If the engine is "dry" and flat between 2k to 3k rpm, raise the fuel level." Factory Pro.

If you haven't read their CV Carburetor Tuning Procedure, do it! The knowledge you'll gain from one page will be worth its weight in gold...if that could be measured. :dunno :evil
 
#28 · (Edited)
#1 pilot jet went clogged on me!

This is what I get for letting the new bike sit for weeks on end without riding it and when I do only riding it 10 miles then parking it again. I had been noticing that < 3,000 RPM operation was getting annoying and erratic and I found out tonight why. The damn pilot jet hole for #1 was completely covered over. The ZXF advice of using a fine piece of wire did the trick. After starting it, the engine RPM was still bobbling about, so I hooked up the CarbTune to discover that clearing the jet made 1&2 off sync. Putting them back in line made the left and right bank off, so I put them back in line.

Took her for a spin. Wow, what a difference! Much much better. :rofl

All is right in the world again.

EDIT: No doubt about it, she's running fine below <3K again. Took the bike out to clear the carbon out, 273 miles worth. Feels good.
 
#31 ·
Just got my Carbtune from England. My home made manometer is sheet. Finally going to do it properly here.
 
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