Author Topic: TB sync - can't balance left and right  (Read 9498 times)

Offline Shawzy

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TB sync - can't balance left and right
« on: May 28, 2011, 01:04:52 pm »
Attempting my first TB sync on 2008 C14 (14000km or 8750m).

Got the carbtune-pro and 90deg driver.  Getting to that center adjustment screw is tough - never mind getting the rubber cap off #2.  Fingers still bleeding.

My issue is that turning the center screw does not seem to balance left and right.

Readings before any adjustments @ 1100rpm fully warm:
1-2-3-4 : 27-28-26-24

After three full turns out of center screw @1100 rpm:
1-2-3-4 : 30-32-30-26

No matter what direction i turn the center screw, the difference in the highest value on each bank (in my case between #2 and #3) is always 2.  I am sure i am on the screw as change does occur with each turn, just not the desired change.

I am bit nervous about continuing, for fear of backing the center screw right out (do not want to go there).

How 'exact' is exact, exactly?  Should i be able to get #2 & #3 equal to each other or is there a deviation acceptable? 






Offline Shawzy

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Re: TB sync - can't balance left and right
« Reply #1 on: May 28, 2011, 01:36:36 pm »
Ok - for whatever reason I got things balanced.  Walked away, took a break, went back and made a single turn in and bang, success.

On first attempt I must have had the c14 idling for 15-20minutes trying to get that center screw, I kept checking she stayed at 1100rpm and adjusted as needed, not sure if this contributed to my issue or not.

All of my readings are now on the high side, ie: 29-30-30-27.  I will attempt bleeder screw adjustment to get them in range (25+/-1).




Offline Shawzy

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Re: TB sync - can't balance left and right
« Reply #2 on: May 28, 2011, 03:16:36 pm »
I need someone with a good understanding on the TB Sync to chime in here. 

After syncing both left and right (ie. 1/2 with 3/4) all 4 of my tb's were not in spec.  They were all on the high side.  The manual states to "balance 1 and 2" and then "3 and 4" with bleeder screws.  Ok fine. Done. Still not in spec, all too high.  Manual doesn't cover what to do next, so I assumed that adjusting each bleeder screw to bring down each tb into spec was the next step. 

This got me thinking - why do we bother with the centre screw in the first place, if we could use the bleeder screws to put all tB in sync with each other and within spec?  Am i making this too complicated?  Is the center screw meant as a 'gross adjuster' and the bleeders 'fine tune'?

If one can adjust all bleeder screws so all TB are bang on 250mmhg is this not the point - what am I missing?

« Last Edit: May 28, 2011, 04:29:46 pm by Shawzy »

Offline Tactical_Mik

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Re: TB sync - can't balance left and right
« Reply #3 on: May 28, 2011, 05:22:21 pm »
 :popcorn:
T.S.R.

Offline B.D.F.

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Re: TB sync - can't balance left and right
« Reply #4 on: May 28, 2011, 05:55:25 pm »
Yes, you could think of the balance screw between the two sets of throttle bodies as the 'course' adjustment and the air bleed screws as the 'fine' adjustment as that is sort of how it works out. To be honest, I do not know why there is a balance screw, as you mention all four T.B.'s could be synch'd with the air bleed screws.

I can't tell from your posts but after each adjustment you should tap the throttle just a little bit to bring the engine RPM up and especially, reset all the throttle body throttle plates against their respective stops. Just adjusting the balance screw and watching for change will not work very well. But you also have to be careful not to 'zing' the throttle too hard as there will be a strong vacuum generated when you close the throttle and you do not want to pull fluid (especially mercury if you have mercury 'sticks' (manometers) ) into the throttle bodies from the top of the manometer tubes. So a gentle tap on the throttle followed by perhaps 5 or 10 seconds to let everything settle down and stabilize and you will notice a change after each turn of the balance screw.

You also have to tap the throttle slightly when turning the individual air bleed screws just to reset all the vacuum levels in all the throttle bodies. Also this adjustment is tricky because as you adjust any one screw, the other three T.B.'s will change and the changes may NOT be the SAME for all three. So you are trying to hit a moving target. The method is to make small moves and generally move toward an even vacuum reading.

Not sure what Kawasaki recommends but I think it is something like 5 cm of mercury difference between all four. With some tweaking you should be able to get all of them within 2 cm of mercury, and perhaps a tad batter but 1 cm is a lot to ask for in my opinion. Note that each reading is really only good for one throttle setting, temperature, etc. because when something like the idle speed changes, so will the relative T.B. vacuum balance.

As far as the actual value of each vacuum reading, you cannot control that- physics does. At a given RPM and a given set of conditions (temp., air / fuel ratio, humidity, and several others) there will be a specific pressure drop across the throttle bodies where the throttle plates are restricting flow (and causing the engine to idle). You can adjust the ratios but not the total amount; if you raise one value, the other three will make a corresponding drop and the sum will be the same within a reasonable idling range. The actual vacuum value is more indicative of engine efficiency (volumetric efficiency) and condition and even that is not a very good way to measure in my opinion. My advice is to ignore the actual value as long as it is not a long way from the factory spec. say, 10 cm of mercury or more. Just balance the individual cylinders relative to each other and call it great; trying to hit a particular value is not going to work and will drive you crazy trying.

Glad to hear you made out OK with the whole thing. Tasks like this are not nearly as scientific as, say, balancing a wheel and tend to be a 'hocus pocus' or best result kind of adjustment like steering a boat on the water rather than a precision setting.

Brian



I need someone with a good understanding on the TB Sync to chime in here. 

After syncing both left and right (ie. 1/2 with 3/4) all 4 of my tb's were not in spec.  They were all on the high side.  The manual states to "balance 1 and 2" and then "3 and 4" with bleeder screws.  Ok fine. Done. Still not in spec, all too high.  Manual doesn't cover what to do next, so I assumed that adjusting each bleeder screw to bring down each tb into spec was the next step. 

This got me thinking - why do we bother with the centre screw in the first place, if we could use the bleeder screws to put all tB in sync with each other and within spec?  Am i making this too complicated?  Is the center screw meant as a 'gross adjuster' and the bleeders 'fine tune'?

If one can adjust all bleeder screws so all TB are bang on 250mmhg is this not the point - what am I missing?
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Offline Shawzy

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Re: TB sync - can't balance left and right
« Reply #5 on: May 28, 2011, 07:49:53 pm »
Brian your response is most appreciated. I was starting to go rather nuts analyzing the whole thing.

I read on a few other boards that some 4 cylinder owners sync the TBs at 5k or even 7k rpm and are not concerned about idle.  This actually makes more sense to me, I would rather have things smoothed out at cruising range (3k-4k) then at idle. Any thoughts on this method?

Offline B.D.F.

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Re: TB sync - can't balance left and right
« Reply #6 on: May 29, 2011, 04:53:50 am »
The synch. applies mostly to idle. At idle the air passage around the throttle plate is extremely small, and so is the air bleed but the bleed size is enough to have significant impact on total flow so. As the throttle is opened, the opening area increases extremely quickly as does airflow; even at something like 1/8 throttle, the air bleeds are insignificant compared to the amount of air flowing through the throttle bodies so you can't synch. them at once the engine is doing any appreciable work. You may be able to synch. them at 4K RPM on the centerstand but even that won't do you much good because the throttle will be open much less than it will at the same engine speed while going down the highway due to increased load.

The reason a throttle body synch. is done at all is because of the extremely small air passages open to the engine at idle; any differences in throttle plate angle, diameter, any wear in the throttle bore even measuring less than one- thousandth of an inch will make a difference at idle. Those same differences become irrelevant at larger throttle openings and in that condition, the fact that all the throttle bores are the same nominal size and the throttle plates are at approx. the same angle relative to each other guarantees synchronization.

I synch. mine at idle and when finished, I run the engine up slowly to maybe 7K RPM just to make sure no one throttle body is significantly different from another. Not to adjust them at that speed, but if there are major differences, there is probably an intake leak somewhere, or a cracked airbox seal, etc.

Brian



Brian your response is most appreciated. I was starting to go rather nuts analyzing the whole thing.

I read on a few other boards that some 4 cylinder owners sync the TBs at 5k or even 7k rpm and are not concerned about idle.  This actually makes more sense to me, I would rather have things smoothed out at cruising range (3k-4k) then at idle. Any thoughts on this method?
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Offline Shawzy

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Re: TB sync - can't balance left and right
« Reply #7 on: May 29, 2011, 07:52:41 am »
What you are saying make sense in regard to air volume passed by bleed screws compared to through the tb itself beyond idle conditions.

This suggests to me that one should only perform a tb sync only when idle is noticeably off, regardless of mileage or age or mods to the machine. If that's true the tb sync seems like a big PITA if the end result is a smoother idle and nothing more.

If tb sync only notably effects engine running characteristics at idle how does tb sync effect bar vibes at higher throttle?  I was lead to believe vibe issue could be solved by tb sync.

Thanks for helping me appreciate the intricacies of our fuel system :)



Offline B.D.F.

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Re: TB sync - can't balance left and right
« Reply #8 on: May 29, 2011, 08:40:51 am »
It has been my experience that TB synchs are not very effective on most bikes although some types benefit from reduced idle vibration from having it done. One example that I know of is a Yamaha FJR (easy Bob, this is serious, not a jab); it is commonly recommended that they be done and quite a few owners claim they are noticeably smoother afterward. But idle is about the limit of the effect, not much benefit going down the road at 50 MPH or similar.

In the olden days of multiple carbs., it was generally the linkage between carburetors that changed over time and synch'ing them made a noticeable difference because of this mechanical change (wear, movement). Today due to the simplicity of the throttle body's construction including one throttle shaft and very precise machining those needs are more or less gone but the process of T.B. synching lives on. Just my opinion but I suspect that a lot of people who do one or pay to have one done on C-14s find improvements because they really want to find the improvement. Sort of like if I charged 100 customers $500 each for a new muffler that was really more restrictive than the original, a large percentage of the customers would still feel the 'improvement' in power, especially if the new muffler was considerably louder because louder = faster.

I have synched my bike twice, the first time I <might> have made an improvement in the balance on the gauge but I certainly moved the differences around. The second time there was a noticeable imbalance between the two sets (1 & 2 and 3 & 4) and I did correct that and again, I really didn't notice any improvement although I did have to adjust the idle down in speed a bit.

By the way after thinking about it I think the reason the balance screw is in the center of the Throttle bodies is because the mfg. didn't want to run a fixed throttle plate rod through all four T.B.s. It would require much higher precision in aligning the T.B.s in the first place and would invite binding and sticking with nothing more than thermal expansion. Using one rod through two T.B.s would not present much of a problem by comparison because the rod itself would be less than 1/2 as long. So they used two throttle plate rods and connected them using a spring loaded connector that will allow for thermal expansion. It also requires that it be adjusted to bring the two sets of throttle plates into alignment and would be subject to vibration wear, which is probably why that was the only thing that changed on my bike between the synch's.

Brian

What you are saying make sense in regard to air volume passed by bleed screws compared to through the tb itself beyond idle conditions.

This suggests to me that one should only perform a tb sync only when idle is noticeably off, regardless of mileage or age or mods to the machine. If that's true the tb sync seems like a big PITA if the end result is a smoother idle and nothing more.

If tb sync only notably effects engine running characteristics at idle how does tb sync effect bar vibes at higher throttle?  I was lead to believe vibe issue could be solved by tb sync.

Thanks for helping me appreciate the intricacies of our fuel system :)
Homo Sapiens Sapiens and just a tad of Neanderthal but it usually does not show....  My Private mail is blocked; it is not you, it is me, just like that dating partner said all those years ago. Please send an e-mail if you want to contact me privately.

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Offline stevewfl

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Re: TB sync - can't balance left and right
« Reply #9 on: May 29, 2011, 04:22:18 pm »
i've put some miles on mine and have found no reason to sync the carbs...errr...throttlebodies
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Offline VirginiaJim

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Re: TB sync - can't balance left and right
« Reply #10 on: May 29, 2011, 05:46:56 pm »
Strangely enough, neither have I...
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Offline MAN OF BLUES

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Re: TB sync - can't balance left and right
« Reply #11 on: May 29, 2011, 06:19:19 pm »
+3
well, I did install auxilairy hoses out to the left side for future use while I was preparing to do my TB synch, but when I put the gages to her it was spot on.... soooo at least I have the aux hoses with plugged ends, sitting right on the spot for future use, when so desired....

oh, did you get the part about "installing hoses and routing them over to an access point" on the left side of the frame....for future use.....???

yeah, not that I would want to try to get to those nipples every stinkin time I decided to check.... so for $3 in hose, it's an easy job to toss the gages on....getting to the screws, well, thats another thing.

hint: Install hoses, routed to the left side of the frame, for future use. ;)

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Offline Wild_Bill

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Re: TB sync - can't balance left and right
« Reply #12 on: May 30, 2011, 02:37:31 am »
+3
well, I did install auxilairy hoses out to the left side for future use while I was preparing to do my TB synch, but when I put the gages to her it was spot on.... soooo at least I have the aux hoses with plugged ends, sitting right on the spot for future use, when so desired....

oh, did you get the part about "installing hoses and routing them over to an access point" on the left side of the frame....for future use.....???

yeah, not that I would want to try to get to those nipples every stinkin time I decided to check.... so for $3 in hose, it's an easy job to toss the gages on....getting to the screws, well, thats another thing.

hint: Install hoses, routed to the left side of the frame, for future use. ;)
I ran mine to a mounting block that I made up

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Offline VirginiaJim

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Re: TB sync - can't balance left and right
« Reply #13 on: May 30, 2011, 06:56:39 am »
My best Toody.....oooh, oooh, I like that idea.  Most excellent in fact. 
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Offline B.D.F.

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Re: TB sync - can't balance left and right
« Reply #14 on: May 30, 2011, 08:29:16 am »
And that is really nice too. A great way to tie up the vacuum hose ends and prevent them from flailing around under the fairing.

Brian


I ran mine to a mounting block that I made up

Bill
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