Anyone use twinmax for carb sync on a KZ?

Carb sync should be the last step in a complete tune-up, because a proper sync depends on valve clearances within spec, strong properly timed spark, fuel levels within spec, perfectly clean carbs, and decent gasoline.

And it's best to have installed brand new spark plugs as per FSM designation.

If sync is attempted under circumstances other than above, it may likely be a wasted effort, regardless of the type of sync equipment being used, or skill level or experience.

Paying a shop to do all the prep (valves; ignition; carbs) in addition to the sync could get quite expensive.
Owners capable of doing the prep are usually also capable of syncing the carbs.

While some shop techs are absolutely fantastic, there are also plenty of horror stories.

When carbs are cleaned and properly set up and synced, and always fed gasoline through a good aftermarket in-line fuel filter, the carbs usually remain in serviceable condition for a long time, and without needing constant fiddling.

Good Fortune!

Classic case of improper/inadequate damping on the circuit and/or plumbing.

You can do quite a bit to smooth out the movement by using proper damping on the tubing, but it's still going to take all day doing two cylinders at a time.

I think it's time for someone to make a four cylinder, digital-readout, manometer requiring no liquids or any other moving parts.

How many inches of static presure are we dealing with?
:idea: I work with hvac controls for a living, and its not that uncommon for me to demo an air handler with at least four differential presure sensors on them. All I would need then is a 40 dollar PLC, and the wifes laptop:idea::idea::idea:

Tomolu5 wrote: How many inches of static presure are we dealing with?
:idea: I work with hvac controls for a living, and its not that uncommon for me to demo an air handler with at least four differential presure sensors on them. All I would need then is a 40 dollar PLC, and the wifes laptop:idea::idea::idea:

The normal vacuum for a KZ650 is 19 - 24 cm Hg with no variance greater than 2 cm Hg between cylinders. Other bikes may be different, but I suspect they are relatively close to those numbers. Ed

The normal vacuum for a KZ650 is 19 - 24 cm Hg with no variance greater than 2 cm Hg between cylinders. Other bikes may be different, but I suspect they are relatively close to those numbers. Ed[/quote]

Okay, So if I am reading this Converter correclty, It says that 22 cm Hg is .289 st atmosphere, Which im guessing means inches of water, So I will have to see, but I think the sensors we use may work, The range is a bit sensitive for them, But I don't really care about the specific reading, but more that they are even.

Am thinking If I used the type with a readout, A power supply is all that would be needed, but even with no readout, four cheapo multimeters(or borrowed good ones) would do in a pinch. I do however like the idea of a screensized realtime readout across the garage though! :evil:

www.alpscontrols.com/Product/ProductDeta...2&xsf=9&ProdID=64054






They would be a bit pricey at $160 each
But I have literally thrown dozens of used ones in the dumpster :pinch: wheres that hitting oneself in the head emoticon I heard mentioned the other day.
It may take a while(gotta wait for a demo job), but I will come up with these babies, and will compare them to the motion pro that I have yet to try.

Wow, looks like I've been missing a bit of excitement here.

Thanks RockMan for the pointers on the sync tools.

And Patton, yes, I did complete all or at least most of the items you mentioned for the bike to be tuned correctly.

- I installed new spark plugs verifying the right clearance for them. Verified that I got good spark out of those plugs.

- I got lucky and have an electronic ignition system on this bike. Cleaned up everything and lubed the advancer while I was at it.

- Cleaned all the electrical connections I could find with a electric contact cleaner.

- Cleaned each of the carb's and jets again and again using a carb cleaner, boiling them in vinegar water etc. etc. etc.

- Only letting in the best quality fuel through an in-line fuel filter.

- Did do a complete bench carb sync this last time (
- slider height at less than 1mm for each carb
- slider height with choke engaged using the throttle screw
- slider position flush with top of bore on full throttle
- air screw setting of 1 3/8 turns on each carb
- set fuel level using a clear tube for each carb per spec
- Using mostly stock carb jets except for the float valve and assembly.

The only thing I did not do was to check the valve clearances. I was going to dig into this if I was unable to get a decent idle going. The compression on each cylinder is pretty good (~170-~180psi).

In fact, this last time, I got the idle going pretty good and my bike was riding very smooth compared to my first test run before all the tune-up. However, I wanted everything to be "perfect" and got excited when a friend let me borrow the carb sync tool. And not doing it right messed up the slider heights and idle again. So I'll be doing all of the tune-up one more time including attempting the carb sync correctly based on the instructions you provided in the cheap sync tool doc.

Thanks again for all your inputs. Keep those ideas coming.

Tomolu5 wrote: The normal vacuum for a KZ650 is 19 - 24 cm Hg with no variance greater than 2 cm Hg between cylinders. Other bikes may be different, but I suspect they are relatively close to those numbers. Ed

Okay, So if I am reading this Converter correclty, It says that 22 cm Hg is .289 st atmosphere, Which im guessing means inches of water, So I will have to see, but I think the sensors we use may work, The range is a bit sensitive for them, But I don't really care about the specific reading, but more that they are even.

Am thinking If I used the type with a readout, A power supply is all that would be needed, but even with no readout, four cheapo multimeters(or borrowed good ones) would do in a pinch. I do however like the idea of a screensized realtime readout across the garage though! :evil:[/quote]

I may be wrong, but I believe 22cm Hg = about 118 inches H2O. Here's a converter link. I figured 22 cm = 220 mm and plugged that into the converter.

www.conversion-website.com/pressure/mill...o_inch_of_water.html

I may be wrong, but I believe 22cm Hg = about 118 inches H2O. Here's a converter link. I figured 22 cm = 220 mm and plugged that into the converter.

www.conversion-website.com/pressure/mill...o_inch_of_water.html [/quote]

Something must be off there, 118 inches is a giant, huge number, the walls of the carbs may collapse if subjected to that kind of vacuum. Pretty thick stainless duct systems in the labs that I work in are only rated for 4-6", and anywhere near that would take a team of clydesdales to open the doors on the airhandlers. I can get an analog guage to check it(only for ranging purposes). I just used the converter app that cam on my phone

Edit: That is .29 in atmospheric presure(or vac), Which is what we express in inches of water, perhaps there is some mix up between the scientific world and that of control system guys??? :blink:

I have wired some pretty large air handlers, and have never seen a static sensor ranged higher than 4.5-5 inches, not saying they arent out there, but they are fairly extreme if they are

The guage will get me in the ballpark though

sorry for hijackin, will start thread upon collection of parts

650ed may be right. I'm guessing you are referring to atm or atmospheres.

www.nodc.noaa.gov/dsdt/ucg/

22cm Hg = 0.2894 atm
0.2894 atm = 9.8130 ft of water
9.8130 ft = 117.75636 inches

That's a lot of water.

And it's fine that my thread is being used to come up with a better solution for sync gauge. Hijack it all you want.

"atm" is an "atmosphere" i.e. equivalent to the standard air pressure at sea level. Chances are I've never seen cm-Hg as a unit of measure before inches Hg (Hg is mercury) is pretty common though, from back in the days when barometers were all filled with mercury, you just measured how far it moved. I'd say everyone's probably right about that just being a failure in communications somewhere.

1atm = 14.696 psi (Atmospheric pressure.)
1atm = 29.92 inch Hg


You can never produce more than 29.92 inches of mercury (14.7 psi) of vacuum, as measured on a "gauge pressure" vacuum gauge. Most common gauges we use are "gauge pressure" type, which basically means pressure (or vacuum) compared to atmosphere.

Since the atmosphere is only about 15 psi (relative to a perfect vacuum), that is the most vacuum one can generate in a pump, engine, etc. With a perfect vacuum inside the carb, the pressure on the outside of the carburetor is about 15 psi at most.

Now, you can create more vacuum if you are in a pressurized environment, but not in normal, sea-level, atmosphere.