Factory Setting for airscrew adjustment

[RCinNC]

I originally posted this in the off-idle stumble thread (and thanks RonH for replying there), but stuff tends to get overlooked in a 34 page thread, so I deleted my post there (so I wouldn't be cross posting) and I'm posting my question here. If the mods feel like this should be moved back there, I understand.

I've done multiple throttle body synchs using the CarbTune since I've owned my bike. There came a point where I was having some difficulty getting the TB's to synch up, so I decided to try the method used to fix the off idle stumble and see if that made a difference. It did, and I was able to get the throttle bodies synched. However, this got me to wondering. When they set the airscrews at the factory, one throttle body is made the standard (on my bike it's the left), and you're supposed to synch the other one to the standard. My question is, how do they determine at the factory what the airscrew adjustment is on the standard throttle body? The off-idle stumble fix is based on turning out the standard airscrew 3/4 turn factory setting, so do all the screws on the standard throttle body have the same setting from the factory? Doesn anyone know what the standard setting is? The screw can be turned all the way in until it's flush with it's seat, so is the standard setting determined at the factory by turning the screw all the way in and then backing it out a specific amount? Theoretically, a guy could buy a used S10 that already had this fix, decided he wanted to try it, and end up turning out the standard further than recommended in this fix. So, what's the factory setting for the standard? RonH suggested the factory setting was for the standard airscrew to be turned all the way in; can anyone verify this?

 

[WJBertrand]

In my case the standard one was the right one and it was fully seated clockwise. I opened it 1/2 turn and then synced the left one to match as best I could. Can’t say I noticed much difference though.


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[Don in Lodi]

Upon getting a new to you bike, to do a tbs for a base line, all that's needed is to have one needle, either needle, to be fully, lightly, seated then backed out the half to 3/4 turn. The seated needle, the standard, has usually got a spot of white paint applied at the factory. If the paint is visible, use that one. They want the very least amount of extra air going down the throttle bore they can manage. Extra air is measured and extra fuel gets injected. Extra fuel makes the emissions police all uptight. It used to always seem to be one side that was closed down. I'm pretty sure that was mostly coincidence. What they do is close the needles steadily, evenly, until one or the other seats. That's it, that's as little extra air as can be adjusted out and still have the throttle bodies pulling equal amounts of air. If they could close both down fully and have everything still pull evenly they would.

 

[RCinNC]

Thanks guys. Next time I do a throttle body synch, I'm just going to return the standard TB airscrew to the fully seated factory setting and work the TB sych from that point. Kind of like a "reset to zero".

 

[fredz43]

M my recollection is that back at the beginning of this thread when discussing TB balance, it was discovered that S10's in Europe and perhaps the rest of the world came with the reference TB screw backed out 3/4 of a turn, while USA bikes came with the reference TB screw closed. When someone tried backing the reference TB screw out 3/4 turn like those bikes came from the factory and then balancing to that new reference, there was an improvement in off idle running. On the 2 S10's that I have owned, I used the 3/4 turn reference balancing method on my 2012 model when it was discussed on this thread and saw some improvement. When I bought my second S10, a 2014, I did that initially and have continued that way with all TB syncs on it.

 

[cyclemike4]

I have a 2012 that I bought new. Both of my screws were turned all the way in to bottom.

 

[RCinNC]

M my recollection is that back at the beginning of this thread when discussing TB balance, it was discovered that S10's in Europe and perhaps the rest of the world came with the reference TB screw backed out 3/4 of a turn, while USA bikes came with the reference TB screw closed. When someone tried backing the reference TB screw out 3/4 turn like those bikes came from the factory and then balancing to that new reference, there was an improvement in off idle running. On the 2 S10's that I have owned, I used the 3/4 turn reference balancing method on my 2012 model when it was discussed on this thread and saw some improvement. When I bought my second S10, a 2014, I did that initially and have continued that way with all TB syncs on it.

I did the same thing, even though I never experienced the off-idle stumble that was the reason for the fix. It was during a re-reading of the thread with the off-idle fix that I began wondering what exactly the factory setting was; the thread said to turn it out 270 degrees, but it didn't say 270 degrees from fully seated (unless it did say that and I missed it somewhere). That got me wondering whether the factory standard was the same for every bike; I figured that it must be, if every bike could be adjusted in the same manner. Because I had had some issues getting the throttle bodies balanced in the past, I wanted to be able to reset to zero next time I did a synch, and knowing what the factory setting for the standard TB airscrew is will help out with that.

 

[RCinNC]

I have a 2012 that I bought new. Both of my screws were turned all the way in to bottom.

Did it run normally with them both screwed all the way in, or did you have to adjust them?

 

[cyclemike4]

no it ran horrible. It ran well as long as you were accelerating. If you held a steady throttle it surged and it often died when coming to a stop or even just slowing down. It also experienced very high engine temperatures if rode slow. that would be 30 miles per hour or slower. Temperature would reach 235 to 239 degrees and would not come down till the speed was taken back up. I tried the 3/4 turns out and it was better. I then tried 1 turn out and better. I have them set at believe it or not one and three quarter turns out and it was waaaaaaaaaaaaaaaaaaaaay better! I have rode it almost 50,000 miles with them set that far out and I have no intentions of ever turning them in. No fouled plugs. No hard starts. I have not been around any bikes with flashed ecu's and they may be way better than mine but it runs really good above 2000 RPM. Below that it still has a funny hit on the power. I think that would be solved if I knew how to set the idle up a bit. it just seems to have trouble getting the crank and counter weights spinning from that low RPM. That is about a 1000 at idle. I just do what works for me so I have no idea what other bikes at different sea levels will do with the screws set that far out. I have been from the gulf of Mexico to the mountains of Wyoming and it did fine.

 

[RCinNC]

Mine ran fine from the factory, and I never had any issues with low rpm smoothness. When I did a TB synch a while back, it seemed like I was having to dial out the non-standard TB pretty far in order to balance them. I was getting a little concerned that I was going to run out of adjustment room on the non-standard TB, which prompted my to want to reset to factory and start over next time.

Which makes me ask another question: what is actually getting out of adjustment in between throttle body sychs, that they have to be adjusted periodically? Obviously something is changing in the throttle body. or else an adjustment wouldn't be necessary. The airscrews feel like they're spring loaded, so it doesn't seem like they would easily move.

 

[cyclemike4]

O.K. here is my shade tree mechanic explanation of the situation. I'm sure one of the sharp forum members here will help me tell you the most correct story behind it all. I will do my best though. the motor itself is drawing in the air through the throttle body or (carb) and that amount of air it can effectively pull in on the intake stroke is different between cylinders of the motor. Example the valves are out or the rings worn. there could also be issues with the butterfly's in the throttle bodies or slides and or butterfly's in the carbs on older bikes that cause a change in air flow as well. Knowing this engine is pretty reliable as far as mechanics go I don't think the usual rider will have issues with that. I guess it is good practice to check those settings from time to time especially after a valve adjustment.

 

[Gigitt]

Throttle body adjustment screws when screwed in all the way does not mean they are at a standard balance point of Zero.
Now the Reference screw does not have a factory set point equal across all bikes - you cannot assume that screwed all the way is the correct Zero point.

The factory sets the Reference screw to what they want the cylinder running at. then balance it with the other screw.
They adjust the screws till the factory gets the emissions and tuning they want.

So with all our stumblings and low rpm fueling issues...

You have to SET the REFERENCE screw to something. This then is the ZERO reference for tuning your bike.
The Balance screw can then be adjusted PLUS or MINUS a number of turns (against the reference zero) to get the correct equal vacuum reading.

The Reference screw does not have the same Zero point on each bike, and that the forum suggested 1/2 to 3/4 turn out from fully seated is a good starting point to balance the throttle bodies.

Because each bike is different, the engines wear differently, ring and valves, compression, spark and injector fouling, carbon build up all affect engine efficiency over time... regular TBS keeps the bike running nice.

 

[RonH]

I think the way they do it, at least in the USA is turn both screws in, then they run the engine. Which ever needs changed to balance is then opened. If no balance issues, I can see where both may be turned in seated, but can't imagine they would do it to make someones life hell, as in won't idle/overheats ect. I think the whole sync thing is blown up like a balloon. I finally synced my 2012 at 30,000 miles, and it needed no adjustment. Since then, got the Harmonizer, so enjoy playing with it, but playing with is near zero as on mine 1/8 turn at most to sync at most when I check.

 

[Nikolajsen]

The factory sets the Reference screw to what they want the cylinder running at. then balance it with the other screw.
They adjust the screws till the factory gets the emissions and tuning they want.

???
Do you really think that factory starts up every engine, for fine tuning this?

 

[Checkswrecks]

The 2010-2013 bikes are different than the 2014-2018 Gen2. If people want to write about what worked for them, PLEASE tell if it is a Gen1 or Gen2. My memory of number of turns and such is similar to Fred's.


With any engine, ALWAYS start by finding what the stock settings were, to return to when things go wrong. Count the number of threads to close each screw and return it exactly to how you found it before anything else. WRITE THESE NUMBERS DOWN preferably in the owners manual, or some other place that you won't lose them.


Most manufacturers run motors before installation, but not for tuning. It's all quick connects and just to make sure they run, shift, etc.


The manufacturers have worked since the days of Edward Deming to minimize variability in everything. They know where to set the first screw to get the needed emissions with the second screw. They haven't spent time tuning individual engines since fuel injection became common.

 

[RhodeTrip]

In my case the standard one was the right one and it was fully seated clockwise. I opened it 1/2 turn and then synced the left one to match as best I could. Can’t say I noticed much difference though.


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Mine was the same.
Jim

 

[Nikolajsen]

Most manufacturers run motors before installation, but not for tuning. It's all quick connects and just to make sure they run, shift, etc.
The manufacturers have worked since the days of Edward Deming to minimize variability in everything. They know where to set the first screw to get the needed emissions with the second screw. They haven't spent time tuning individual engines since fuel injection became common.

Exactly my thought
And I know for sure (at least for some years ago), that BMW did not even fire up the engine. They just spinn the wheel, and shift up through the gear, and down again. Thats it..

 

[RonH]

I'm not sure they start the engines to determine which screw needs tweeked, but regardless of how they do it, in some fashion they can tell one screw should be turned out slightly to balance the TB. If no balance issues both screws could be closed.
I know on GL1800 Honda, they run every motorcycle on a dyno before it leaves the factory. I've seen youtube videos on that.

 

[RCinNC]

I just got done changing my air filter, so I decided to recheck the throttle body sync while I was at it. I had marked the original position and the new position on the standard airscrew back when I did the off-idle adjustment, so I decided to turn the screw all the way in and count the turns. Turns out that the original position of the standard screw was fully closed. So, my experience mirrors others' in this thread; my standard would have been completely closed when I got the bike. So, I reset to zero, and then I backed the screw out by 1/2 turn. The throttle bodies were synced from there, and this time I have more adjustment room on the non standard throttle body than I did before.