Throttle Body Balance Question...

[Top Ten]

I have a question about balancing and/or adjusting the throttle bodies (throttle body balance, TBB).

First, a little background. I have performed TBB's and carb syncs in the past on other bikes and have done so now on my 2018 non-ES ST. In general I know the theory behind TBB but would appreciate further insight on the proper way of doing it.

I originally had a problem with my ST stalling at idle. The bike appeared to idle normally but would frequently die upon take-off. Sitting at a red light, get the green, properly apply clutch and throttle and the bike would die. Using the starter, it would start right back up. Very annoying. And dangerous.

After getting the run-around from my local dealer, and having read about opening-up the TB screws on the ST, I bought a Motion Pro Sync Pro manometer to check my TB's. I determined the painted TB screw (on my bike, the left one) was closed. I opened the left one up one full turn, and then balanced the right one to that. Problem solved. It has not died since that adjustment and I am happy with the way the bike runs ( I have also performed a re-flash).

Now for my question. I recently did my 20K oil change and other maintenance, and as a part of that routine I performed a TBB. The TB's were balanced at idle. But then I decided to increase the RPM's up to see what the balance looked like at operating RPM's and noticed they did not stay balanced. Balanced at idle, not balanced at 3-4K RPM, but not a lot of imbalance. I think opening up the closed TB's has cured my idle problem; should I now balance the TB's at what would normally be my operating RPM's? It seems to me it would be more important to have the TB's balanced in an RPM range they operated in the most, not just at idle.

If you have experience with this issue, let me know what you think.

 

[jbrown]

When I first balanced the throttle bodies on my bike (using a "harmonizer"), I took a ride with the harmonizer connected. The balance is way different under load than at idle. If I adjusted to balance under load, the idle balance was way off, and the idle was rough. So I just set it at idle. Note that this is just an air bleed adjustment. The throttle bodies share a common shaft, and there is no ability to really synchronize the two valves like on carbureted bikes. I consider the TB sync to be an idle only adjustment, although others have indicated substantial changes in under load riding. In my test, I could not tell any difference under load at all, even with the sync *way* out of balance.

 

[ballisticexchris]

I recommend starting from scratch. The Super Tenere gets the left one adjusted to right throttle body to balance. I ran the right one out 3/4 of a turn and balanced the left one to that. No more stalling at idle. I also keep my bike in sport mode most of the time which helps immensely.

 

[RCinNC]

I've only ever done the throttle body adjustment at idle. I don't believe there is any other adjustment you can make other than that. I have a Morgan Carbtune that I use to do the adjustment, and when you rev the engine in neutral with the Carbtune attached, the levels aren't exactly the same between both throttle bodies.

I had a hard time getting the throttle bodies to balance the first time I did the adjustment with the throttle bodies at the factory settings. I found some helpful info in this thread: https://www.yamahasupertenere.com/index.php?threads/airscrew-adjustment-to-fix-off-idle-stumble-and-throttle-body-sync-w-pigtails.1973/

I didn't have the off-idle stumble, but when I did the adjustment to the air screw that's described in this thread, I was able to synch up the throttle bodies with no issues.

 

[~TABASCO~]

Keep in mind that 97% of the bikes have the (R) TB with the white painted mark on them, this is the master. If you happen to have the (L) TB with the white mark this one would be the master. Keep an eye out for that.

Assuming the (R) has the white paint mark, then you SYNC the other side at idle..... Ive always been taught, told, you can slightly increase the RPM's to "upset" the RPM's but then let it idle and adjust again at idle. These bikes tend to bounce around from 1025-1200 RPM's at idle.. Factory says 1100 I believe.

Make sure the bike is up to operational temps- 180-200 while performing the sync. I sync and adjust my bike about once a year.

 

[Jlq1969]

I have a question about balancing and/or adjusting the throttle bodies (throttle body balance, TBB).

First, a little background. I have performed TBB's and carb syncs in the past on other bikes and have done so now on my 2018 non-ES ST. In general I know the theory behind TBB but would appreciate further insight on the proper way of doing it.

I originally had a problem with my ST stalling at idle. The bike appeared to idle normally but would frequently die upon take-off. Sitting at a red light, get the green, properly apply clutch and throttle and the bike would die. Using the starter, it would start right back up. Very annoying. And dangerous.

After getting the run-around from my local dealer, and having read about opening-up the TB screws on the ST, I bought a Motion Pro Sync Pro manometer to check my TB's. I determined the painted TB screw (on my bike, the left one) was closed. I opened the left one up one full turn, and then balanced the right one to that. Problem solved. It has not died since that adjustment and I am happy with the way the bike runs ( I have also performed a re-flash).

Now for my question. I recently did my 20K oil change and other maintenance, and as a part of that routine I performed a TBB. The TB's were balanced at idle. But then I decided to increase the RPM's up to see what the balance looked like at operating RPM's and noticed they did not stay balanced. Balanced at idle, not balanced at 3-4K RPM, but not a lot of imbalance. I think opening up the closed TB's has cured my idle problem; should I now balance the TB's at what would normally be my operating RPM's? It seems to me it would be more important to have the TB's balanced in an RPM range they operated in the most, not just at idle.

If you have experience with this issue, let me know what you think.

is that the air that can be regulated with the screw, is only for idling ... (the butterflies of the bodies are completely closed and the "minimum air for idling enters below those butterflies through the screws ... only for idle) .... when you accelerate to 3-4 rpm, the air enters through the throttles, not through the screw. A very marked vacuum difference between the two bodies when the engine is turning at 3-4 k rpm, "could be indicating" a difference in the valves regulation

 

[Top Ten]

I recommend starting from scratch. The Super Tenere gets the left one adjusted to right throttle body to balance. I ran the right one out 3/4 of a turn and balanced the left one to that. No more stalling at idle. I also keep my bike in sport mode most of the time which helps immensely.

Thanks. On my bike the left TBB screw was painted white. I take that to mean the left one was the base setting. On my first balance on the ST I turned the base screw out 3/4 of a turn, only because that is what I read on the internet. I have since tried one full turn out, and that worked even better. I don't think the 3/4-turn rule should be considered a hard-and-fast rule. I generally run touring mode; maybe I should try sport mode a little more. Maybe try sport mode during a TBB.

 

[Top Ten]

Keep in mind that 97% of the bikes have the (R) TB with the white painted mark on them, this is the master. If you happen to have the (L) TB with the white mark this one would be the master. Keep an eye out for that.

Assuming the (R) has the white paint mark, then you SYNC the other side at idle..... Ive always been taught, told, you can slightly increase the RPM's to "upset" the RPM's but then let it idle and adjust again at idle. These bikes tend to bounce around from 1025-1200 RPM's at idle.. Factory says 1100 I believe.

Make sure the bike is up to operational temps- 180-200 while performing the sync. I sync and adjust my bike about once a year.

FYI, there is no doubt; the left-side TBB screw on my bike is painted white. But the factory tells us not to adjust the base setting, so the issue of which screw is the base screw is really moot; I am going to open either screw to one full turn and then balance the other one. In my case, I opened the left side one full turn and balanced. I do appreciate your advice.

 

[~TABASCO~]

FYI, there is no doubt; the left-side TBB screw on my bike is painted white. But the factory tells us not to adjust the base setting, so the issue of which screw is the base screw is really moot; I am going to open either screw to one full turn and then balance the other one. In my case, I opened the left side one full turn and balanced. I do appreciate your advice.

I believe the factory has a "tool" that will let them know what side to set as the best base/white paint mark. This screw is always shut and the other side is "adjusted".... (I have found no rhyme or reason for the left and right, but the white mark is the master.) I always screw this back in to make sure it is seated, then unscrew it 3/4 (your case 1) turn out and then go to the unpainted side and SYNC the other side. Should be good.... Most bikes I see are 10-12 points out. My "world record" on someone else's bike was 34-36 points out.....
Because of the age of some of these bikes now im seeing corrosion on the brass air screws in the aluminum TB bodies... If you have ANY resistance at all, make sure to use some type penetrating lube on the screws and let them sit... DO NOT round off or break the brass air screw slot..... DON'T DO IT ! (Ive run into this 'stuck screws' more and more often)
One more note: Ive only seen this twice ever but Ive seen the air screw almost vibrate out of the TB. It almost had fallen out on one of these two examples. The bike was probably performing like crap. Anyone reading this that have never touched or looked at these screws, I SUGGEST you look at them with a flash light at the very minimum. If you have 50-70-90K miles on your bike and the TB have never been SYNC'ed, I would also suggest finding a friend with the tool and doing this job on some random weekend. It will really help around idle and over all performance. While your there, back out the white painted side 3/4 or 1 turn and SYNC the other side........

 

[Jlq1969]

Thanks. On my bike the left TBB screw was painted white. I take that to mean the left one was the base setting. On my first balance on the ST I turned the base screw out 3/4 of a turn, only because that is what I read on the internet. I have since tried one full turn out, and that worked even better. I don't think the 3/4-turn rule should be considered a hard-and-fast rule. I generally run touring mode; maybe I should try sport mode a little more. Maybe try sport mode during a TBB.

If you've already gotten used to T mode ... switching to S mode may be abrupt for you. Why don't you try to adjust the throttle cable “a little”? .... maybe the feeling improves a bit.

 

[Dons 1911]

Great info here guys, Thanks! Here is a follow on question (or two) I'd like to point towards @~TABASCO~ .

The Service Manual say to "adjust synchronization of the Fuel Injection", Item 5 on Page 3-1 of my Service Manual, LIT-11616-27-50. It asks for this to be done every 4k miles. The only instructions I can find for synchronization is to Sync the Throttle Bodies. Are they talking about the same thing?

Also, the service manual calls out for the Throttle Grip Free Play adjustment to have 3.0-5.0 mm of free play. My last bikes felt best with almost zero free play. Thoughts on this? Thanks!

 

[~TABASCO~]

Great info here guys, Thanks! Here is a follow on question (or two) I'd like to point towards @~TABASCO~ .

The Service Manual say to "adjust synchronization of the Fuel Injection", Item 5 on Page 3-1 of my Service Manual, LIT-11616-27-50. It asks for this to be done every 4k miles. The only instructions I can find for synchronization is to Sync the Throttle Bodies. Are they talking about the same thing?

Also, the service manual calls out for the Throttle Grip Free Play adjustment to have 3.0-5.0 mm of free play. My last bikes felt best with almost zero free play. Thoughts on this? Thanks!

I think 4K is probably to often for sync. Also agree- I virtually have no play in the throttle. (Minimum play, but certainly not tight). Make sure to check lock to lock when adjusting throttle cables. You do not want it to pull on the cable when turning the bars, double check this.

 

[Top Ten]

I've only ever done the throttle body adjustment at idle. I don't believe there is any other adjustment you can make other than that. I have a Morgan Carbtune that I use to do the adjustment, and when you rev the engine in neutral with the Carbtune attached, the levels aren't exactly the same between both throttle bodies.

I had a hard time getting the throttle bodies to balance the first time I did the adjustment with the throttle bodies at the factory settings. I found some helpful info in this thread: https://www.yamahasupertenere.com/index.php?threads/airscrew-adjustment-to-fix-off-idle-stumble-and-throttle-body-sync-w-pigtails.1973/

I didn't have the off-idle stumble, but when I did the adjustment to the air screw that's described in this thread, I was able to synch up the throttle bodies with no issues.

Yep. I remember reading through that post a year or two ago. Thanks. I got a lot of good info from it. I think that is the post that convinced me to tackle the TBB issue in the first place.

 

[Top Ten]

It appears this thread may have run it's course for now. I appreciate the feedback from everyone. My primary question about checking TBS at higher RPMs has been answered. For anyone reading this in the future, I will try to summarize this thread:

(1) I titled this post a "Throttle Body Balance Question." I should have titled it a Throttle Body Sync Question (TBS).

(2) Performing a TBS is relatively simple, given you have the tools. If you have problems with your idle, or take-off from idle, you should consider a TBS or a TB Adjustment. And by adjustment I mean turning air screws that the factory does not intend for you to turn (the one painted white).

(3) TBS and adjustments can be different without load and with load.

(4) A TBS only affects the idle; the sync between TB's at speed and load cannot be readily adjusted and are not affected by a TBS. TB's that are synced at idle may not be synced at higher RPMs.

(5) The factory painted my left throttle body screw white, which means that is the base screw and should not be adjusted. On other bikes (the majority) the right screw is painted white.

(6) Sometimes the TB screws can suffer corrosion. Make sure you do not damage those screws. If you feel abnormal resistance to turning you may want to use some penetrating oil (WD-40) and wait a day and try again.

(7) Although many posts on this subject recommend a 3/4 turn out for the painted screw, I found my bike runs better at one full turn out. Your bike may vary. I recommend you try different settings.

 

[Clawdog60]

Great info here guys, Thanks! Here is a follow on question (or two) I'd like to point towards @~TABASCO~ .

The Service Manual say to "adjust synchronization of the Fuel Injection", Item 5 on Page 3-1 of my Service Manual, LIT-11616-27-50. It asks for this to be done every 4k miles. The only instructions I can find for synchronization is to Sync the Throttle Bodies. Are they talking about the same thing?

Also, the service manual calls out for the Throttle Grip Free Play adjustment to have 3.0-5.0 mm of free play. My last bikes felt best with almost zero free play. Thoughts on this? Thanks!

jeez I'm 5 times over due.

 

[RCinNC]

Man, I missed that interval in the service manual. Last time I synchronized mine was in March 2018 at 44,486 miles. I just went over 80,000 in May. I can't imagine why they'd need to be synchronized with every oil change. Maybe that air screw tends to vibrate loose. I've certainly never noticed any difference in how the bike runs (though I probably should drag out the Carbtune and make up for my neglect).