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#996168 - 09/05/17 12:43 AM TB Sync. Who remembers this detail?  
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EffBee Offline
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OK, so I bypassed the TB sync last service on my 1100RT because I was in a hurry. And now that I have to do it, I've forgotten one piece of crucial info.

Naturally, you want both sides to show equally on your manometer (I use Mercury Sticks). But if one side MUST lead the other, is it the left barely leading the right or the right barely leading the left?


Cary, Gleno, Rodger, Paul,
Godspeed, my brothers.
We will never forget you.


Teach your children about taxes. Eat 40% of their ice cream cone.

Do you have a MotoReflective Reflective Kit (Link) for the rear of your BMW?
#996182 - 09/05/17 02:58 AM Re: TB Sync. Who remembers this detail? [Re: EffBee]  
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roger 04 rt Offline
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Because the O2 sensor is registering the average of the two cylinders it doesn't matter.

#996189 - 09/05/17 10:37 AM Re: TB Sync. Who remembers this detail? [Re: EffBee]  
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dirtrider Offline
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Originally Posted By: EffBee
OK, so I bypassed the TB sync last service on my 1100RT because I was in a hurry. And now that I have to do it, I've forgotten one piece of crucial info.

Naturally, you want both sides to show equally on your manometer (I use Mercury Sticks). But if one side MUST lead the other, is it the left barely leading the right or the right barely leading the left?


Morning EffBee

Roger is correct about the o2 averaging cylinders so riding in closed loop it makes little difference.

If you are looking for accuracy then don't use that mercury stick setup. Just make a simple H2o U tube manometer. If you use an H2o U tube then just getting it close is WAY better than looking perfect on the mercury sticks.

A slight blip on the mercury sticks (1/2") is over 6" on the H2o manometer.

In any case, to answer your question-- you want both sides as close a possible with both sides lifting of their idle stop screws at the exact same time then hitting the WOT stops at the very same time.

On the BMW 1100 boxer (IF) you have to end up with one side leading the other then you want the L/H side to be the leader as the L/H side has the TPS so the L/H side supplies the initial fueling info.

Or you can test it yourself-- with the engine running just tug on the R/H cable at the TB cam, the R/H side gets only air with no added fuel until the RPMs come up a little.

Now tug on the L/H side TB cable as that gives you air plus a little added fuel to both sides.


D.R. ___
Sent from my rotory dial wall phone!
#996194 - 09/05/17 11:44 AM Re: TB Sync. Who remembers this detail? [Re: EffBee]  
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roger 04 rt Offline
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Good Morning DR,

Your advice about chucking the mercury sticks in favor of the manometer is sound. Myself, trying to implement the "lead" protocol sounds difficult and will likely lead to an inferior sync. In my mind, it would go something like this (shorthand):

--get the engine hot, all cables loose
--get a perfect balance at idle using only the BBS, and hot idle at 1100 rpm.
--tighten all cables to BMW spec
--slowly rotate the throttle between 1100 and 2500 rpm, adjusting whichever cable needs to be slightly loosened (so that no cable has all its slack removed) to achieve coincident lift off of the throttle plates AND best balance at all points between 1100 and 2500 rpm. The proviso for the "lead" idea would then be: "but if you can't get a perfect lift-off at 1100, the vacuum on the right should lag (higher column) the vacuum on the left, as long as that doesn't lead to a poorer balance at other points between 1100 and 2500."

It sounds impractical at best, and is not an objective of the sync procedure. A better objective that's not in the BMW procedure, that you've often recommended, would be to have both throttles lift off the stops at the same moment and hit the stops at WOT at the same moment.

Last edited by roger 04 rt; 09/05/17 11:45 AM.
#996310 - 09/07/17 02:19 PM Re: TB Sync. Who remembers this detail? [Re: EffBee]  
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EffBee Offline
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Thanks, all. Here's how it went.

Both adjustment screws hit their stops. So I slide in a piece of cellophane paper between the screws and stops. Each is taped to a string and has a hefty fender washer on the other end of the string. With the engine off, I slowly roll on the throttle while I watch the washers. They fall evenly to the ground. If not, I adjust the throttle stop screws until they do.

Next I set the idle balance using the BBS (which I've pulled and cleaned, including where they sit in the throttle bodies). I ended up at 1.5 out on one side and 1.75 on the other.

I've got a Euro-style throttle housing made for the thumb screw throttle tension adjuster, with one of the world's last remaining Schneider Fil-A-Lever throttle locks in place of the thumb screw. Poor man's cruise control, but I've been using one for 200,000 miles and I'm used to it. This allows me to set the throttle around 3,000 rpm and sync while the engine runs at that speed (with a fan blowing on each side, of course). I do use Mercury sticks and this time I nailed it. Perfect with nary a difference. I see that a homemade manometer with ATF is more accurate. And I can make my own dampers as I've got Delrin rod and a table-top lathe, a similar mill, and an indexed drill set. But when I get the mercury sticks right, the engine purrs.

I know I'll have to dispose of the mercury some day. But until then, this works. I'm taking it for a test ride this morning before putting the Tupperware back on, and if there's any hesitation, I'll have to come back and let the right side lead the left a little. That might only involve a slight reduction in the lock nut tension.

Headed from CA to UT and CO, so a nice sync pays off on long days. Thanks to all for their help.


Cary, Gleno, Rodger, Paul,
Godspeed, my brothers.
We will never forget you.


Teach your children about taxes. Eat 40% of their ice cream cone.

Do you have a MotoReflective Reflective Kit (Link) for the rear of your BMW?
#996388 - 09/08/17 05:13 PM Re: TB Sync. Who remembers this detail? [Re: EffBee]  
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Trobinson Offline
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Originally Posted By: EffBee
Thanks, all. Here's how it went.

Both adjustment screws hit their stops. So I slide in a piece of cellophane paper between the screws and stops. Each is taped to a string and has a hefty fender washer on the other end of the string. With the engine off, I slowly roll on the throttle while I watch the washers. They fall evenly to the ground. If not, I adjust the throttle stop screws until they do.


I'm pretty sure DR and Roger would agree with me here, but you don't want to mess with the throttle stop screws unless absolutely necessary. These set the closed throttle angles for proper air volume at idle and is especially important on the left side since the TPS is on that side. If you move the left throttle stop screw then you've also changed the idle voltage of the TPS. Roger did a great write up on the zero=250mv procedure for this setup. Doing otherwise you may get a good balance for a while, but I think you'll experience other issues at some point as I did when I adjusted my stops improperly.


Tom
San Antonio, TX

Growing old is mandatory, growing up is optional.

1996 R1100RT

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