Airscrew Adjustment to fix off-idle stumble and Throttle Body Sync - w/ pigtails

[GM4X4]

I'm new to doing a throttle body sync. If you sync at idle would it still be in sync at higher RPM? In other words if I were to sync at 1100RPM and my idle perfect would the throttle body still be in sync during average highway driving RPM of 3500RPM? If it would not be in sync during driving would it be better to have a little stumble at idle and the throttle body in sync at higher RPM/driving speeds?

 

[Firefight911]

I'm new to doing a throttle body sync. If you sync at idle would it still be in sync at higher RPM? In other words if I were to sync at 1100RPM and my idle perfect would the throttle body still be in sync during average highway driving RPM of 3500RPM? If it would not be in sync during driving would it be better to have a little stumble at idle and the throttle body in sync at higher RPM/driving speeds?

Adjust TBS is only truly effective down low by way of adjusting the air screws. As the rpm goes up, the influence of the air screw goes down. The butterflies are pretty much locked together on the S10 as they are motor driven so there is no way to do this........though I admit to not having studied the service manual specific to this topic and this bike yet.......

If you are experiencing stumble, etc. at higher rpm, it is typically related to something other than an air screw sync issue. One would look at a coil stick, spark plug, or injector usually.

Now, on the boxer, 12 series, BMW you actually adjust the cable sync and TBS is done at around 4000 rpm on that bike but this is different than what we have here.

 

[colorider]

Again acronyms decieve me. What is CoSTOC?

A "gathering" in Colorado of the (Honda) ST Owners Club - STOC.

Here is the info on the event.

 

[colorider]

ColoradoSTOC ST Owners Club. This is an online club started back in 1994 for owners of ST1100s by Derek Katt.

Actually Derek Catt (STOC 001), along with Charlie Woods (STOC 002). George Catt (STOC 004), Dereks dad, is still very active in STOC.

Now, back to our Airscrew discussion!!! Sorry for the thread-drift!!!!

 

[DuMar]

Re: Airscrew Adjustment to fix off-idle stumble and Throttle Body Sync - w/ pigt

I'm finding this topic very interesting, as I also have noticed a fair bit of snarkyness in the lower rpm range. I recall Wasp relating how much he enjoyed just putting her in 1st gear and letting her tow him around all over the place. Mine doesn't do that - it chugs and surges and needs a lot of input to keep it smooth.

I really wanted to have this resolved prior to my first extended off-road trip coming up on Sept 9th, but don't have my service manual yet or a manometer. Can someone please tell me what range and units are needed on the manometer to perform the TBS?

Thanks,
Mike

 

[GM4X4]

Adjust TBS is only truly effective down low by way of adjusting the air screws. As the rpm goes up, the influence of the air screw goes down. The butterflies are pretty much locked together on the S10 as they are motor driven so there is no way to do this........though I admit to not having studied the service manual specific to this topic and this bike yet.......

If you are experiencing stumble, etc. at higher rpm, it is typically related to something other than an air screw sync issue. One would look at a coil stick, spark plug, or injector usually.

Now, on the boxer, 12 series, BMW you actually adjust the cable sync and TBS is done at around 4000 rpm on that bike but this is different than what we have here.

Thanks for the info. That makes a lot of sense. That also answers alot of my questions about TBS on the Tenere.
My first bike was a KLR650 so I never had to worry about this but now I would nned to know because I like to do my own work/maintenance.

 

[JRTEN]

Me too, wont go crazy adjusting stuff until the bike has time to settle in. ::026::

 

[colorider]

Devin,
I went shopping yesterday for the hose, barbed fittings, etc. Only took 7 stops before I got everything and even then, could not find 5/32 end caps. Had to settle for 1/8". Went to Autozone, Ace, JAX, Home Depot, JAX again, Lowes and finally Advance Auto.

Did the "T" section a little different than you as I was afraid the one hose would kink. Also, not sure if I ended up with the same spring clamps as you.

Ran out of time to try anything, but need to try and find a flex-shaft screwdriver before I proceed anyway.

Thanks for all the good info!!!

Rod

 

[3putt]

First, big thanks for this tech work and help on both the CO settings and the TBS.

I did the CO Diag mod first. I have the normal states bike, and my OEM settings were "0" for both cylinders. I changed them both to +6.

Moved on to the TBS. I found all the 5/32" stuff (hose and caps) at pepboys. I used a T on the left side after cutting the existing connection in half. Ran both hoses out the right side for easy connection to my DIY sync tool. I checked at OEM settings of airscrews and right side was high. Backed off to 270 degrees and still about the same. Adjusted the left cylinder to balance. With my DIY tool, you must adjust slowly and allow the ATF to catch up in the clear line, takes a few seconds to register new setting.

The green ziptie marks the level mark and right cylinder, after starting the engine the right pulled up. I adjusted the left side airscrew to make them equal and at the ziptie again.

tbs.AVI

 

[tomatocity]

To ALL.

Are your vacuum line extensions of equal length?

I did not use vacuum caps but I did use plugs. The plugs are metal with a flat head. The reason for not using the vacuum caps was the hardware store did not have them.

 

[Yamaguy55]

First, big thanks for this tech work and help on both the CO settings and the TBS.

I did the CO Diag mod first. I have the normal states bike, and my OEM settings were "0" for both cylinders. I changed them both to +6.

Moved on to the TBS. I found all the 5/32" stuff (hose and caps) at pepboys. I used a T on the left side after cutting the existing connection in half. Ran both hoses out the right side for easy connection to my DIY sync tool. I checked at OEM settings of airscrews and right side was high. Backed off to 270 degrees and still about the same. Adjusted the left cylinder to balance. With my DIY tool, you must adjust slowly and allow the ATF to catch up in the clear line, takes a few seconds to register new setting.

The green ziptie marks the level mark and right cylinder, after starting the engine the right pulled up. I adjusted the left side airscrew to make them equal and at the ziptie again.

tbs.AVI

I like my mercury synchronizer because it responds instantly. The eviro-thugs are searching for me as I write this in seclusion for owning such a thing. Just don't chop the throttle suddenly from higher RPM, or you could ingest the mercury. The TB air screw adjustment should be done after the CO adj. One will affect the other. If you do have access to the mercury one (and others may do this as well) you can run up the RPMs and watch the two TBs track each other. I noticed that I could still affect sync at higher throttle openings and RPMs, it was just exaggerated from the idle settings. So I went hi-lo-hi-lo on the RPM to get a good job. Took a little longer, but worth it.
It has improved the off-idle response and reduced the vibration. I also went from an average of 44-45 MPG to 47-48; same roads, same riding style. Some of that could be the engine continuing to break in.
I would suggest revisiting this at 5K, and then 10K miles, to see if it remains the same. Once you get a feel for it, you can then decide how often it needs to be checked.

On my old '77 XS650, if I touched up the points and checked the sync once a month, it ran like a champ. I had it down to about fifteen minutes. It completely eliminated the problems these engines were known for. Modern CDI/EFI bikes don't need this level of attention, but they aren't cars, either.

Nice wooden canoes.

 

[colorider]

(and others may do this as well) you can run up the RPMs and watch the two TBs track each other. I noticed that I could still affect sync at higher throttle openings and RPMs, it was just exaggerated from the idle settings. So I went hi-lo-hi-lo on the RPM to get a good job. Took a little longer, but worth it.

Hmmm, perhaps I could of fine-tuned mine better. I set it at idle, revved it up a few times and then rechecked at idle - but did not try to actually set it at a higher RPM. I was using the "Harmonizer" and it did deviate from "0" at higher RPMS.

 

[Twisties]

I like my mercury synchronizer because it responds instantly. The eviro-thugs are searching for me as I write this in seclusion for owning such a thing. Just don't chop the throttle suddenly from higher RPM, or you could ingest the mercury. The TB air screw adjustment should be done after the CO adj. One will affect the other. If you do have access to the mercury one (and others may do this as well) you can run up the RPMs and watch the two TBs track each other. I noticed that I could still affect sync at higher throttle openings and RPMs, it was just exaggerated from the idle settings. So I went hi-lo-hi-lo on the RPM to get a good job. Took a little longer, but worth it.
It has improved the off-idle response and reduced the vibration. I also went from an average of 44-45 MPG to 47-48; same roads, same riding style. Some of that could be the engine continuing to break in.
I would suggest revisiting this at 5K, and then 10K miles, to see if it remains the same. Once you get a feel for it, you can then decide how often it needs to be checked.

On my old '77 XS650, if I touched up the points and checked the sync once a month, it ran like a champ. I had it down to about fifteen minutes. It completely eliminated the problems these engines were known for. Modern CDI/EFI bikes don't need this level of attention, but they aren't cars, either.

Nice wooden canoes.

Mercury is a very poor choice of liquid for three reasons:

At 13+ times the density of water, and even more times the density of oil or ATF it has 13 or more times less sensitivity. for instance if you can reliably discern a 5 mm difference in fliud levels in your manometer that 5 mm will correspond to more than ten times the difference in pressure with mercury than it will with water or a less dense fluid. Another way of putting it: The height difference in your column will be greater the less dense your liquid is. The height difference (sensitivity) is proportional to the density of the liquid.

Mercury destroys aluminum, even very small amounts of mercury can damage aluminum.

Mercury is toxic, both to the touch and the vapor from open mercury. If it get's loose, you will never get it all collected again, and will be getting exposed to small amounts. It is not advisable to use something toxic when a non-toxic or low-toxic alternative is available.

 

[3putt]

And we used to play with it as kids, jeeze.

 

[simmons1]

And we used to play with it as kids, jeeze.

I was thinking the exact same thing ;D

 

[Twisties]

And we used to play with it as kids, jeeze.

Me too. Couldn't you tell?

 

[slipangle]

I'm curious as to what is happening with the left side throttle body. Does anyone know the purpose of the sensor that the vacuum line ties into?

It concerns me because I don't have a factory manual yet, and ended up winging the throttle body synchronization today with my newly acquired Harmonizer. I didn't make the pigtails like SpeedStar did, so I ended up just pulling the vacuum line off of the mystery sensor in order to connect the harmonizer to the left side throttle body, leaving the sensor disconnected from the engine's vacuum. Would leaving the sensor out of the loop negatively affect the adjustments that I made?

Everything seemed okay during my test ride afterwards. Before synchronizing, I adjusted the CO setting by +6 via the diagnostic mode, and then made the 270 degree adjustment to both of the air screws. I was suprised by how much I had to tweak the left side throttle body in order to sync it with the painted right side. While the Harmonizer only showed it as being 6 millibars out of adjustment, both before and after the 270 degree adjstment, I ended up having to close the unpainted screw about 180 degrees in order to get it to zero, making me suspicious that my leaving the mystery sensor out of the vacuum system has thrown off the adjustment.

 

[RMac]

Reading this thread with interest. Can anyone explain exactly what opening the airscrews 270 deg actually does? Same question for the CO setting and what impacts it has on engine and emissions? Does the service manual explain these things?

 

[tomatocity]

Last week we did the airscrew adjustment and the engine seemed to run well except... when normally accelerating in 1st gear @ approx 3,000 RPMs the engine RPM would increase quickly. I have not ridden it for three days and needed to ride. Tonight 6pm the engine seemed to run well and smooth except for the 1st gear acceleration increase. I rode into cool darkness and hills. The engine started to stumble like it was running lean or rich. Then I thought affected by long downhills. Stopped for a burger at In & Out Burger. When leaving I realized the engine was running poorly overall. Final 20 miles were on the freeway at a constant 3500 RPMs and the engine ran inconsistantly. Filled up at 141 miles and averaged 43.85 MPG which is less than the usual 48 MPG. When I get a chance I will check for vacuum leaks and the balance of the throttle bodies. I have not set the CO levels to +6 though have plans to do this.

Suggestions! Advice! Appreciated!

 

[Yamaguy55]

Reading this thread with interest. Can anyone explain exactly what opening the airscrews 270 deg actually does? Same question for the CO setting and what impacts it has on engine and emissions? Does the service manual explain these things?

The service manual does not cover these things. The reason for that would being regulations compliance. They are not going to tell you to adjust out of spec. We're sort of doing an end run around the excessively lean nature of the stock setup. Most newer FI bikes tend to be this way stock.

That said: think of the CO adjustments as the mixture screws on the carburetors. Think of the air screw adjustments as the linkage adjustments to sync the carbs on a multi cylinder engine. That isn't what is really going on, but that is the equivalent in effects to the way the engine runs.

The opening of the air screws to 3/4 of a turn for a starting point allows more air to bypass the throttle plates of the TBs. My guess is, due to the continuous nature of this, the O2 sensors are correcting for the additional airflow. Note I said "guess on this. I can only guess, as I have no hard data, just an overview on how the FI works. This is also why if you have a permanent hose setup and get vacuum leaks, you'll get a "check engine" light: you have more air bypassing the throttle plates than the system can compensate for. I don't have a permanent setup for just that reason; it doesn't take long to hook up anyway. It takes longer to get to the adjustment screws with the tank/side panel removal/etc. I don't expect to be in there often, maybe once a year at most.