BMWMCCWA

This post is created as a specific reference to syncing the throttle bodies on BMW twins.

What's 'syncing throttle bodies'?

Broadly speaking, a carburetor or throttle body has a valve (often referred to as a butterfly valve) inside which controls the flow and amount of air that is directed into the cylinder. If more than one carburetor/throttle body is present, both butterfly valves MUST operate equally to ensure equal air is added to all cylinders.

Typically, an idle adjustment is required that is separate to an on-power throttle condition.

The outcome of this post is to have an exhaustive reference to synchronizing the BMW throttle bodies / carburetors using the 'Harmonizer' tool.

What's a 'Harmonizer'?

The Harmonizer tool is manufactured by Grok, a member of the ADV Rider forum, and engineer, and is available for purchasing occasionally at the following ADV Rider forum topic.

ADV-RIDER website: http://advrider.com/index.php?threads/h ... ax.701625/

Feel free to add value / constructive comments to make this a useful reference for us all.

A collection of links to other websites is valid.

But do remember that websites come and go. So please reference the original author/source/website in these articles for just those times when that website/content disappears from the internet.

In all engine types, preparation for this task requires that no inlet nor exhaust leaks are present. Ignition / points adjustments are set correctly. Throttle body synchronization is the last engine tuning task to be performed, after all other adjustments are completed.

In order:

• First: Valve / tappet adjustments should be made on a COLD engine.
• Last: Throttle body / Carburetor syncing should be made on a ROAD HOT engine.

A large cooling fan should be placed in front the the bike/engine, switched on, and flowing cooling air over the cylinders and oil cooler.

Sections: However similar, please keep the various models separate for clarity.

• R1200 LC
• R1200
• R1200 C (The single throttle body version obviously doesn't require syncing...)
• R1150
• R1100
• Air Heads (per designation)

AIR HEADs

Source: Grok, AdvRider member, engineer and manufacturer of the Harmonizer

http://advrider.com/index.php?threads/h ... 25/page-12

Post #234

There are 3 types of adjustments for balance and carb tuning.
1. Carburetor idle mixture
2. Idle balance and RPM combination.
3. Higher-RPM balance.

Do a careful valve adjust first. It helps immensely for smoothness.
Warm the engine to operating temperature, then shut it off.
Put a BAF (big ass fan) on it while doing the adjustments.

The first thing we are going to do is a rough idle balance and RPM adjustment. This will make sure the carbs are working roughly equally and are running on the idle jets instead of the main jets. This is in preparation for adjusting the idle mixture. If the bike is generally running well, this step 1 may not be necessary.

STEP 1. ROUGH BALANCE and RPM ADJUSTMENT.
PURPOSE: make sure carbs are contributing roughly equally and are operating on the idle jets by adjusting idle balance and RPM in Harmonizer balancer mode.

Disconnect the vacuum line from the left carb and remove the cap from the right. plug on the Harmonizer hoses and push the red button. After some seconds, the Harmonizer will finish it's calibration routine and stand ready in balancer mode. Put the petcock in prime position (this will bypass and defeat the vacuum shutoff function). Start the motor and blip the throttle a couple of times. Make sure there is a very small amount of slack in the cables. Adjust the idle stop screws (not the idle mixture screws) such that the Harmonizer shows balanced at around 1000 to 1100 RPM. You don't need to be too accurate here. We're going to redo it later. Shut off the motor.

STEP 2. IDLE MIXTURE ADJUSTMENTS
PURPOSE: Optimize idle mixture for each carb by adjusting for max vacuum in Harmonizer gauge mode.

Here's where we adjust the idle mixture for each carb. In the previous step we made sure both carbs were contributing roughly equally and were running on the adjustable idle jets. Disconnect the Harmonizer hose from the right carb and put the cap back on. At this point the Harmonizer should be connected with one hose only, yellow port to left carb. Put the Harmonizer in gauge mode by holding the button pressed until you see "gauge mode" and releasing the button. Start the engine. On the Harmonizer display you will see a left-zero graph and a numeric display that shows vacuum in inches of mercury along with the tach reading. The object is to adjust the idle mixture screw on the left carb such that the vacuum reading is as high as you can make it. Make small adjustments and give the Harmonizer a few seconds to settle after each small tweak. Once you've maximized the vacuum reading for the left carb, shut off the motor. Disconnect the Harmonizer from the left carb, replace the vacuum petcock hose, and remove the cap from the right carb. Connect the Harmonizer yellow port the the right carb. Still in gauge mode, repeat the process of adjusting the idle mixture screw for maximum vacuum on the right carb. Shut off the motor.

STEP 3. FINE IDLE BALANCE and RPM ADJUSTMENT.
PURPOSE: Fine tune idle balance after messing about with the idle mixture adjustments in step 2.

Step 3 is basically a repeat of step 1. The Harmonizer is in balancer mode and both hoses are connected. The object is to adjust the idle stop screws such that the Harmonizer show a balanced condition and the RPM's are within specifications. Shut off motor.

STEP 4: HIGHER RPM BALANCE.
PURPOSE: Adjust relative cable lengths such that the carbs are balanced above idle, while the cables are in control.

Make sure both cables have a small amount of slack - maybe 2mm or so.
Put the Harmonizer in balancer mode if it has automatically turned itself off. Restart the motor.

Adjust the relative cable length by adjusting ONE of the cable adjusters (the right side is traditional) such that the Harmonizer shows a balanced condition at around 3000 RPM or so.

That should do it!

Shut-off motor. Disconnect Harmonizer, replace petcock hose and vacuum cap, shut-off petcock.

Lastly, check and adjust the throttle-hand-grip cable free-play.

R1150 Throttle bodies

Broadly speaking, the R1150 has fuel injection for on-power fueling but retains the 'old' idle mixture screw and butterfly valve adjustments for separate control of idle adjustments.

To that end, an adaptation of Grok's article follows...

Source: Grok, AdvRider member, engineer and manufacturer of the Harmonizer

http://advrider.com/index.php?threads/h ... 25/page-12

Post #234

There are 3 types of adjustments for balance and throttle body tuning.
1. Throttle body idle mixture
2. Idle balance and RPM combination.
3. Higher-RPM balance.

Do a careful valve adjust first. It helps immensely for smoothness.
Warm the engine to operating temperature, then shut it off.
Put a BAF (big ass fan) on it while doing the adjustments.

The first thing we are going to do is a rough idle balance and RPM adjustment. This will make sure the throttle bodies are working roughly equally and are running on the idle jets. This is in preparation for adjusting the idle mixture. If the bike is generally running well, this step 1 may not be necessary.

STEP 1. ROUGH BALANCE and RPM ADJUSTMENT.
PURPOSE: make sure the throttle bodies are contributing roughly equally and are operating on the idle circuits by adjusting idle balance and RPM in Harmonizer balancer mode.

Remove the caps from the left and right throttle bodies. Plug on the Harmonizer hoses and push the red button. After some seconds, the Harmonizer will finish it's 'calibration' routine and stand ready in 'balancer' mode. Start the motor and blip the throttle a couple of times. Make sure there is a very small amount of slack in the cables. Adjust the idle stop screws (not the idle mixture screws) such that the Harmonizer shows balanced at around 1000 to 1100 RPM. You don't need to be too accurate here. We're going to redo it later. Shut off the motor.

STEP 2. IDLE MIXTURE ADJUSTMENTS
PURPOSE: Optimize idle mixture for each throttle body by adjusting for max vacuum in Harmonizer 'gauge' mode.

Here's where we adjust the idle mixture for each throttle body. In the previous step, we made sure both throttle bodies were contributing roughly equally and were running on the adjustable idle mixture screws. Disconnect the Harmonizer hose from the right throttle body and put the cap back on. At this point the Harmonizer should be connected with one hose only, yellow port to left throttle body. Put the Harmonizer in 'gauge' mode by holding the button pressed until you see "gauge mode" and releasing the button. Start the engine. On the Harmonizer display you will see a left-zero graph and a numeric display that shows vacuum in inches of mercury along with the 'tach' reading. The object is to adjust the idle mixture screw on the left throttle body such that the vacuum reading is as high as you can make it. Make small adjustments and give the Harmonizer a few seconds to settle after each small tweak. Once you've maximized the vacuum reading for the left throttle body, shut off the motor. Disconnect the Harmonizer from the left throttle body, replace the vacuum cap, and remove the cap from the right throttle body. Connect the Harmonizer yellow port to the right throttle body. Still in 'gauge' mode, repeat the process of adjusting the idle mixture screw for maximum vacuum on the right throttle body. Shut off the motor.

STEP 3. FINE IDLE BALANCE and RPM ADJUSTMENT.
PURPOSE: Fine tune idle balance after messing about with the idle mixture adjustments in step 2.

Step 3 is basically a repeat of step 1. The Harmonizer is in 'balancer' mode and both hoses are connected. The object is to adjust the idle stop screws such that the Harmonizer show a balanced condition and the RPM's are within specifications. Shut off motor.

STEP 4: HIGHER RPM BALANCE.
PURPOSE: Adjust relative cable lengths such that the throttle bodies are balanced above idle, while the cables are in control.

Make sure both cables have a small amount of slack - maybe 2mm or so.
Put the Harmonizer in 'balancer' mode if it has automatically turned itself off. Restart the motor.

Adjust the relative cable length by adjusting ONE of the cable adjusters (the right side is traditional) such that the Harmonizer shows a balanced condition at around 3000 RPM or so.

That should do it!

Shut-off motor. Disconnect Harmonizer, replace vacuum caps.

Check and adjust the throttle hand grip cable free-play.

A useful addition to the club tool kit?

A very useful addition, some say

At the tuning day, we could not locate the recommended procedure to sync the throttle bodies on the R1150. The bike was running very poorly.
The final result using the Harmonizer was pretty impressive, but the idle speed was a little high. Now that the correct operating procedure is known, that is using 'gauge' mode to adjust the idle, these last small adjustments can be made.

This is the main reason that this thread was started, to gather all this information into one place where it is easy to locate the next time.

R1200

This BMW model is very different to previous incarnations of the BMW twins. It has very complicated computer systems that control the engine exhaust emissions.

The idle mixture is controlled by the engine ECU/computer. The ECU adjusts idle air bypass solenoids by referencing feedback from the lambda oxygen sensor(s) in the exhaust system.

Syncing the throttle bodies is a little more complex and requires that the idle air bypass solenoids are locked in the ROAD HOT position prior to making any adjustments. There are methods for achieving this, but I will have to search out where I read about them before committing the procedure to print.

As far as I can ascertain these solenoids have some influence over the air/fuel ratio up to medium engine speeds. The exact rpm I cannot say. More consideration will need to be given before documenting this procedure.

In the meantime, Jim von Baden (ADV Rider inmate and BMW wizard) has some excellent material on this and other maintenance tasks on BMW twins.

http://www.jimvonbaden.com/Tech_Pictorials.html

He also produces DVDs on BMW twin maintenance which can be purchased from his website. I bought his wheel balancer a couple of years ago. No frills honest service.

His website: http://www.jimvonbaden.com/

His R1200 throttle body sync (using a TwinMax tool): http://www.jimvonbaden.com/R1200_TB_Sync.html

More to come...

Your club has one...

However, the Harmonizer now available at KatDash

http://katdash.com/

How to harmonize your boxer...