Carb sync ? # 2,157.....please help!!!!

[dekberg]

Got my carb sync tool in a couple days ago and went out tonight to sync the carbs. Got a carb sync tool with 4 gauges. Hooked everything up and after warmup and at 1000 rpm idle the gauges are reading at about 7 psi at idle. All gauges are reading this low. Normal is supposed to be at 22 psi (I think). Is this an issue? The bike idles good and I don't seem to have a loss in HP. All gauges are reading the same but that # seems low.:ummm:

**UPDATE: My gauges read in vacuum inches. The guages are reading in a red area that says the following: (late valve timing or leak at intake manifold or heat riser).
My VMAX has 20,000 miles on it and has never had a valve adjustment and the rubber boots around the carbs and manifold are dry and cracked. Could/would these two things be the possible culprit?

Please help!!!!
Thanks,
Darren

 

[unblind]

I don't think that should be an issue.
Look at the Morgan carbtune as well as motion pro, they both read pressure as #cm HG, (I don't know what that stands for).
The Yamaha manual also states "vacuum pressure at idling speed ---- Above 200 mm Hg (7.90 in Hg)"

Your meter is in PSI?

Someone else might chime in with a better response, but I know all carbs should read the same pressure, so sounds like your good.

 

[ninjaneer]

from what i've gathered, i've been led to believe that one shouldn't bother with the absolute readings, because when it comes to synching it's all relative--meaning all carbs should be creating the same amount. this is apparent with the homemade manometers that some folks use, which other then the equilibrium marks have absolutely no other marks whatsoever. however, when it comes to measuring for purposes other than synchronizing, i don't know what that would be.

cmHg means centimeters of mercury.

anyways, haynes says, that the carb synch absolutes are: min intake vaccuum idle = 170 mmHg (or 17 cmHg) and the max diff between carbs = 20 mmHg (or 2 cmHg). quickly converting psi to torr yields 7 psi = 362 mmHg (or 36.2cmHg) so your bike is definitely meeting the minimum. so the question now is: is it too high? i'm sure someone will chime in.

 

[Blurr]

I have a SyncPro. It doesn't have any actual readings, just as Ninjaneer says, 'hash marks'.
http://www.kneedraggers.com/product/653248/Motion-Pro-Sync-Pro-Carburetor-Synchronizer
It does a fine job of allowing me to get them sync'd. for a moment. but they seem to hunt and peck. After I set it then blip the throttle it will settle down and be pretty level. If I just let it run for 5 minutes one bank will start to diverge some. Blip the throttle again and it will settle down for a bit then again start to diverge. This normal?

Btw, is the measure of min and max vacuum important enough for me to invest in a second tool to read it, or is it more wish list item for those (and, it is turning out) obsessed with maximizing your Vmax's perfectness?

 

[21Turner]

Where did you get the carb sync tool and is it very expensive? And is it user friendly?

 

[Blurr]

Mine? ordered it at the local Yamaha shop. In Ak we have to get most small stuff flown up. And they can't fly mercury. As for being usable, yes quite easy to use. Follow the directions and it is pretty strait forward. (I tend to be the guy who reads those directions 3 or 4 times while he is trying to wrap his head around some foreign concept that everyone else takes for granted though. But when i got it, i got it. Hell I read the whole entry on how to change the air cleaner three times. Might be alittle of the whole 'I don't know why I needed to study; I aced the test' thing going on.)


As for price, I seem to remember the number being around 80 bucks delivered sticking in my head. back when I was having the go/no go conversation in my head... Again, Alaska so you will likely end up paying less.

It is pretty limited as to what it tells you. doesn't read actual vacuum just the relative amounts between them. I believe I have read of some other having trouble with them in so far as they have had the fluid get sucked up into the motor. I came close but when one starts to get too close to the top I will adjust another to get them to even up then go back to the first. That seem to help.

:Edit: the link I gave has the price at 86$
also, sorry for hijacking your thread Dekberg.

 

[SpecOps13]

I have a Sync Pro and also a Mercury Manometer. I've tried the Carb Tune and used Gauges. The calibration of each will give different readings. The most important aspect of syncing the carbs is that the sync tool is calibrated first. I hook all tubes or gauges to the lead cylinder and verify that they read the same at the rpm I want to calibrate at. Then I hook them to the individual cylinders and go to that rpm. I know that when all cylinders are set, they are in sync with each other. I don't worry about the actual numerical reading on the manometer or gauge.

Note: I have my Sync Pro set up to run with Marvel Mystery Oil instead of their proprietary fluid. I can actually calibrate it to make final readings anywhere on the scale by varying the amount of air just under the calibration screws of the tool itself...

Good luck,
Dave

 

[CaptainKyle]

here is something good for a newbie that has nothing.http://cgi.ebay.com/ebaymotors/Vmax...rcycles_Parts_Accessories&hash=item2a0fb39e1e

 

[[email protected]]

As noted, measurements in the manual are not PSI which is what you are measuring.

It doesn't matter, just make them all match and you will be good to go.

 

[dekberg]

The gauges I have read in vacuum inches.

I'm at 20,000 miles and have never had a valve adjustment....could this also make the readings low?

The rubber boots around the carbs and manifold are dry, cracked and rotted. I know I need to replace these....could be another cause???

Thanks for the responses so far.

Darren

 

[Fire-medic]

I have a venerable set of Bourdon tube gauges similar to this one:

They are on a sheet metal holder. The directions say, "if the needles are off, (meaning they display different readings when individually hooked to the same source) remove the glass, remove the needle carefully, and replace it so the same reading shows on each, and replace the glass." FYI, a table fork works great for this, just slip the tines under the gauge needle & gently pry-up.

I have used these for many bikes for many years since getting them in about 1980. As has been pointed out, the absolute value is not important, but the differences between gauges is as they should all display as close as possible the same readings. An advantage of the Bourdon tube gauges: no messy liquid to be ingested into the engine from a too-enthusiastic throttle blip.

Here is a tutorial from Motion Pro:
http://www.motionpro.com/motorcycle/articles/view/348/synchronizing_carburetors_and_throttle_bodies/

This one looks very similar to mine:
http://www.motorcycle-superstore.com/1/4/65/21754/ITEM/Emgo-Carburetor-Synchronizer.aspx?SiteID=SLI|Carburetor%20Synchronizer&WT.MC_ID=10010

 

[dekberg]

**UPDATE: My gauges read in vacuum inches. The guages are reading in a red area that says the following: (late valve timing or leak at intake manifold or heat riser).
My VMAX has 20,000 miles on it and has never had a valve adjustment and the rubber boots around the carbs and manifold are dry and cracked. Could/would these two things be the possible culprit?

Thanks again everyone,
Darren

 

[one2dmax]

Carb boots are definitely going to need replaced if the cracks are visible but I'm not sure about the vacuum number as much as even across the board. Valves can also cause poor performance and or sync issues.

Sean

 

[ninjaneer]

I'm at 20,000 miles and have never had a valve adjustment....could this also make the readings low?
Darren

dude, did you skim by my last post, or is it that i misunderstood your readings? you ain't low by my calculator.

...haynes says, that the carb synch absolutes are: min intake vaccuum idle = 170 mmHg (or 17 cmHg) ... quickly converting psi to torr yields 7 psi = 362 mmHg (or 36.2cmHg) so your bike is definitely meeting the minimum. so the question now is: is it too high? ...

 

[RaWarrior]

This is what all of mine looked like pre-sync...borrowed the gauge rack from work. The numbers are in inches of mercury. The best I could get was about a total variance of about .5inHg from the lowest to the highest.

 

[dekberg]

dude, did you skim by my last post, or is it that i misunderstood your readings? you ain't low by my calculator.

Sorry man...didn't ignore your post. The gauges I have aren't real clear on the way it is measuring the pressure. Just searching for as much input as possible.

The gauges are made specifically for carbs....There is a red area on the gauge I'm falling into (around 7) that is marked (late valve timing or leak at intake manifold or heat riser) Then there is a normal area marked "19-22 (normal)". In the VMAX manual the norm is 22 of some kind of measurement. Figured the 22 (norm range) is where the needles were supposed to be. (The only marking on the outside of the gauge by those #s says ?Vacuum pressure?.

Not trying to make mountains out of ant hills here?..but the gauges are syncing all the same. (That seems to be the important part). I?ll replace the rubber boots around the carbs and manifold and see if this makes any difference.

Thanks for taking the time to help out,
Darren

 

[Fire-medic]

I am sure a good mechanic will say, "all systems need to be in good operational order to make carb adjustments." Vacuum leaks from cracked boots falls in that category. Not having properly-adjusted valves is another factor which could prevent you from being able to get the synch OK.

One hash-mark from low to high? Doesn't sound bad to me, but I am not a mechanic. Just an enthusiast.

 

[ninjaneer]

Sorry man...didn't ignore your post. The gauges I have aren't real clear on the way it is measuring the pressure. Just searching for as much input as possible.

nah man, i just didn't want you to start throwing parts at that mole hill. (^_^) good luck, brah.

 

[MR_NST]

just a thought... and its free. take a spray bottle, and lightly mist the boots while the engine is running and the guages are hooked up. does the reading change. if no then your boots are still good. but if the vaccuum readings go up you have found your leak... an old trick. lol its got me out of a few head scratchers.

peace,
evan...

 

[Fire-medic]

Doing the same thing w/some solvent spray can will cause the rpm's to rise, meaning the solvent is being sucked into the intake tract. "A difference you can hear!" Just be careful to do it outside, away from any other source of ignition besides your hot motor...& don't let the solvent puddle. "MR NST" doesn't mention the contents, but I assume he was referring to H2O, safer than solvent. And for those of you who passed chemistry, yes, water is "the Universal Solvent," so how-about "a spray can containing an aromatic hydrocarbon (like carb cleaner)?"

Of course, do this with the airbox in-place.