White screw- throttle body synchronization

[northsouth]

I followed 2 wheel obsession's throttle body synchronization procedure and he stated that the adjustment screw with white paint on it ( very hard to see) is the control which was cylinder # 1 on his bike and you do not adjust that screw, but all others. I finished and all seemed even on the gagues. Riding it I noticed a vibration that wasn't there before, although not terrible. I decided to break it down and check again and got a better view this time and it turns out cylinder # 3 has the paint mark. Crap. Does anybody know how to get this screw adjusted back to where it's supposed to be?

 

[Fred W]

Im assuming that you are talking about your 2016:

If so, the screw with the white dot was the one with the lowest vacuum when all four screws were initially closed (lightly seated) during their factory sync. That one was left fully seated and the others were opened slightly (which relives some vacuum) to match the low one. The idea was that they wanted to add the least possible amount of bypass air, so that the other circuits (ECU controlled cold and warm idle opening of the main butterflies) have the maximum possible range and effect.

To get back to factory settings, just lightly seat the one with the white dot, and the open the other three to make vacuums match.

That said, if you had all of the vacuums matched, that should have resulted in minimum vibration. What you are sensing may just be in your head. These engines do tend to be buzzy at certain rpm ranges, and the amount seems to vary as they age and break in. Since there isnt much we can do about it, I would encourage you to not worry, be happy, and ride on!

 

[northsouth]

Thanks Fred. Yes it is a 2016. I will try this. The vibration is irritating and it was not there before. I will be sure to record my settings this time in case anything different happens.

 

[Kaelaria]

Often times you can just closely look at the paint - line up the marks on the screw head with the sides back where it was. It was most likely fully (lightly) seated.

 

[northsouth]

I looked at that but the entire screw head was white. Turns out I only turned it about 1/4 turn ​out. Lightly seated it, re-synced the other 3 and will see how it feels tomorrow.

 

[bruinFJRguy]

I adjusted my white screw on my old fj09. Panicked, I talked to a tech and was told to not worry about where the white screw was, just to make sure the gauges matched and ride. I only did about another 2k miles after that sync, but all seemed fine.

I suspect you are just freaked out like I was. Match the vacuum and ride.

 

[Uenjoymyself]

I followed 2 wheel obsession's throttle body synchronization procedure and he stated that the adjustment screw with white paint on it ( very hard to see) is the control which was cylinder # 1 on his bike and you do not adjust that screw, but all others. I finished and all seemed even on the gagues. Riding it I noticed a vibration that wasn't there before, although not terrible. I decided to break it down and check again and got a better view this time and it turns out cylinder # 3 has the paint mark. Crap. Does anybody know how to get this screw adjusted back to where it's supposed to be?

Please do let us know how things turn out. I too watched that video and int the comment section Dave states that the reference screw should not be touched because it is calibrated to the ECU and the procedure to re calibrate is complex. I'd like to know if, in fact, this is not the case.

Hope all goes well and you're running smooth once again!

Thanks, Uenjoy

 

[jammess]

Please do let us know how things turn out. I too watched that video and int the comment section Dave states that the reference screw should not be touched because it is calibrated to the ECU and the procedure to re calibrate is complex. I'd like to know if, in fact, this is not the case.

Hope all goes well and you're running smooth once again!

Thanks, Uenjoy

I would really like to know how a throttle body air bypass adjustment screw can be matched to the ECU. I think that would be a pretty good trick.

 

[Uenjoymyself]

Please do let us know how things turn out. I too watched that video and int the comment section Dave states that the reference screw should not be touched because it is calibrated to the ECU and the procedure to re calibrate is complex. I'd like to know if, in fact, this is not the case.

Hope all goes well and you're running smooth once again!

Thanks, Uenjoy

I would really like to know how a throttle body air bypass adjustment screw can be matched to the ECU. I think that would be a pretty good trick.

Perhaps I have it backwards.

According to the video starting at 19:25

And the comment section:

Yanier Olivera

 

[Fred W]

We did a survey of 3rd Gen bikes, and in every case the white painted screw was the one that was left fully closed by the factory. Recreating fully closed is pretty damn easy, if you ask me. There is no magic, or ECU requirements going on here.

Minimizing the bypass air through these air screw passages became important in 3rd Gens when Fly by wire was introduced. With that change, the cold start high idle mechanism and the warm idle speed adjustment screw were eliminated. All idle speed (both cold and warm) is now a function of the ECU opening the main throttle plates more or less to achieve the required cold or warm idle speed. So minimizing leakage air around them means the throttle plates will be open more at warm idle and allow it to regulate properly.

There have been some instances where people have found, over time, that one or more of the other throttle bores had lower vacuum than the reference even when that screw was also fully seated. In that case, the one with the lowest vacuum when they are all fully seated becomes the new reference, and you just open the other three to match it.

One more point: If you still have increased vibration after balancing the vacuums, I would suspect the instrument you are using to balance them. Once you have it well balanced, try swapping vacuum hoses around. 1-2, 2-3, 3-4, etc. If that changes any of the balanced readings then the gauge is your problem.

 

[northsouth]

I considered doing just that. I am using a brand new Carbtune Pro, but it appears that the #2 slide has some resistance. Funny, I had a Carbtune 2 years back and it had the same issue. They say it is not an issue but I don't see how it can't affect accuracy.

 

[RossKean]

I considered doing just that. I am using a brand new Carbtune Pro, but it appears that the #2 slide has some resistance. Funny, I had a Carbtune 2 years back and it had the same issue. They say it is not an issue but I don't see how it can't affect accuracy.

TEE all four lines together and hook them up to a single vacuum source. If the #2 slide has a problem, it will read differently from the other three.

 

[northsouth]

Makes sense. I'll do that.

 

[Fred W]

If you are using a Morgan CarbTune, you need to make sure that the instrument is perfectly vertical so there is minimal friction between the rods and the glass tubes they are enclosed in. That friction would be the most likely reason for variation.

The second most likely reason would be blockage of one of the small orifices that you are supposed to install in the hoses. You did install those orifices, right? If not, RTFM.

 

[northsouth]

If you are using a Morgan CarbTune, you need to make sure that the instrument is perfectly vertical so there is minimal friction between the rods and the glass tubes they are enclosed in. That friction would be the most likely reason for variation.
The second most likely reason would be blockage of one of the small orifices that you are supposed to install in the hoses. You did install those orifices, right? If not, RTFM.

Yes I did. I cut them with a very sharp razor blade to exactly the same length. The unit was vertical (hanging from the left handlebar during the tune). 3 rods bounced and fluctuated the same and the 2nd one didn't fluctuate as much, but screw adjustments raised or lowered it.

 

[Pjotr]

We did a survey of 3rd Gen bikes, and in every case the white painted screw was the one that was left fully closed by the factory. Recreating fully closed is pretty damn easy, if you ask me. There is no magic, or ECU requirements going on here.

Minimizing the bypass air through these air screw passages became important in 3rd Gens when Fly by wire was introduced. With that change, the cold start high idle mechanism and the warm idle speed adjustment screw were eliminated. All idle speed (both cold and warm) is now a function of the ECU opening the main throttle plates more or less to achieve the required cold or warm idle speed. So minimizing leakage air around them means the throttle plates will be open more at warm idle and allow it to regulate properly.

There have been some instances where people have found, over time, that one or more of the other throttle bores had lower vacuum than the reference even when that screw was also fully seated. In that case, the one with the lowest vacuum when they are all fully seated becomes the new reference, and you just open the other three to match it.

One more point: If you still have increased vibration after balancing the vacuums, I would suspect the instrument you are using to balance them. Once you have it well balanced, try swapping vacuum hoses around. 1-2, 2-3, 3-4, etc. If that changes any of the balanced readings then the gauge is your problem.

I, (like Javlin3 (on another thread), have the problem on gen3 2013 FJR that my TB3 has too low vacuum and cannot turn screw any further. Based on above you advice to now use TB3 as reference and adjust, including TB1 with the white paint, to in this case TB3, is that correct? Has anybody had any issues with this change of TB1?
KR/Pjotr

 

[Fred W]

Hello Pjotr,

Yes, I think you have it right. Once any of the channels becomes lower than the rest, just ignore the paint dots and make that channel the reference, left fully closed, and adjust the rest to that level. The key is to balance the 4 channels. The absolute value of the channels matters not at all.

Best of luck,
Fred

 

[Pjotr]

Hello Pjotr,

Yes, I think you have it right. Once any of the channels becomes lower than the rest, just ignore the paint dots and make that channel the reference, left fully closed, and adjust the rest to that level. The key is to balance the 4 channels. The absolute value of the channels matters not at all.

Best of luck,
Fred

Fred,
Thanks. I’ll try it soon.
Pjotr

 

[Pjotr]

Fred,
Thanks. I’ll try it soon.
Pjotr

I’ve synchronized now with cil 3 as reference (fully closed) and adjusted cil1 with white dot. Seems to work so far. Now still trying to understand why idle is still erratic. On higher refs it is very stable. Inclined to change tps, but not convinced yet.

 

[RossKean]

I’ve synchronized now with cil 3 as reference (fully closed) and adjusted cil1 with white dot. Seems to work so far. Now still trying to understand why idle is still erratic. On higher refs it is very stable. Inclined to change tps, but not convinced yet.

Maybe try #3 open a quarter to a half turn and then balance the others to it? I only do a TBS on my 2011 Gen II if I have done major engine stuff - valve adjustment or anything with the throttle bodies. It is rarely off by much and I don't notice any difference before and after. Note: The Gen II does not have a paint dot to designate the "base" cylinder. I start with all out a bit over a half turn from lightly seated.