Author Topic: Carb Sync with an STE Synchro or Hg manometer/vacuum gauge set *  (Read 10398 times)

Offline KoTAOW

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Carb Sync with an STE Synchro or Hg manometer/vacuum gauge set *
« on: December 22, 2007, 04:15:42 PM »
(original page here: Mike Martin's ST1100 Maintenance Tips

Carb Sync with an STE Synchrometer

Most of us use Carb Sticks or the like, but our friend Hans ten Broeke from The Netherlands recommended using the STE SK Synchrometer to synchronize the carburetors.  Ed Lee put together a group buy for purchasing them in Europe through Hans at his website.  (Note: Hans will honor the price he gave for the group buy, though shipping for a single unit will naturally be more expensive.)  If you missed that opportunity, you can now find a source for the meter here in the U. S.  I Googled "carb flow meter" and found this site so you could see what I'm referring to.  (Note: I've never dealt with this company.)  The smaller "SK" version of the meter is the one to use for the ST1100.  (Mike Roell found a knock-off of the device here and he reports it works "just fine for me."  I found another source at this site (usual disclaimers).  The picture is very small, but my guess is that this meter is also a knock-off.

Ed also put together the following write-up for using the device.  The basics of carb sync is covered in the various service manuals.  Ed's instructions point out the difference in using the meter.  The process seems to take a lot less time than with the mercury-filled Carb Sticks.

Ed's Write-up:


Be CAREFUL that you actually LOOK at the rubber pipes on the carbs to be sure you put the SK on the correct pipe.  

As you sit on the bike:

#4 is the carb on your left next to the tank, which is directly connected to the throttle assembly and is not "adjustable" relative to the other carbs, but is adjusted by the idle adjustment knob next to the tank filler cap.

#1 is on the right front.

#2 carb is the front carb on the left side .

#3 is on the right rear.

The rubber tubes that you put the SK into sit on top of their respective carbs, but the OPENINGS to the tubes are on the OPPOSITE SIDE.  Just set an rpm with the adjustment knob (next to the filler) that will assure that each carb is well off any mechanical stops (I used 2000 rpm for an "idle" speed for my tests).  Then plug the SK into the tube for #4 (which opens on the RIGHT rear even though the carb is on the left rear) and take the reading.  Let's say it is 4.0. Now move the SK up to the opening on the right front tube which goes to the carb on the LEFT front, #2 and adjust the screw on the shaft between the two carbs on the left side so that #2 is has the same flow as #4.  Then move the SK to the tube for #1 carb (right front), which opens on the LEFT side at the front, and adjust the forward screw joining the throttles on the right two carbs so the SK reads the same flow as #4 and #2.  Finally move the SK to the tube for #3 (which opens on the LEFT side, rear) and adjust the aft screw on the shaft between the two carbs on the right side to match the flows on the other carbs.

Go back to #4 and check the flow again to make sure it has not changed.  If any of the carbs were way off, it will have changed because the idle speed will have changed.  If #4 is no longer at the original reading then repeat the process as above.  It will be correct after that.  Now readjust the knob for the master idle and button it back up.

As an aside, I removed the bottom part of the airbox to do mine because it was just too hard to see and get the throttle linkage adjustment screws with it in place.  If you DO remove it, remember to replace the little crankcase breather hose connected to the bottom side.  Easy to miss.


After Ed posted his write-up, Hans responded with,

"Hi Ed,

"Nice you like the SK also.

"I only use a thin long, about 10" screw driver and a mini maglite, and don't remove anything at all besides the dummy tank and of course first, the side panels to remove the dummy tank."


Thanks to Ed and Hans for their helpful suggestions.

« Last Edit: December 29, 2012, 11:05:25 AM by Tom Melnik »

Offline KoTAOW

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Re: Carb Sync with HG manometers or vacuum gauge set
« Reply #1 on: December 30, 2007, 05:13:37 PM »
Web page here

Carb Sync with Hg manometer or vacuum gauge set

All you need:

A four column manometer or vacuum gauge set.
A philips screwdriver with 12" long blade.
A plastic T piece such as is used in windscreen washer pipework on your car
(not essential but useful)

1. Warm engine up
2. Remove seat, maintenance covers, tank cover (top shelter), both fairing pockets.
3. Remove the diddy little caps from vacuum tubes from carbs 1,2 & 4.
4. Hook up manometer tubes to vacuum tubes from each cylinder. NB. for
carb #3 you need to remove the vacuum line from the fuel cutoff valve,
attach a short piece of spare tube to the fuel valve, insert T-piece
between this and vacuum tube from carb, and then attach the manometer to
the T piece. (All this does is ensure that you have a vacuum applied to
the fuel cut-off valve whilst synching the carbs so that there is no
possibility of the carbs getting starved of fuel).

5. Start motor, set to fast idle 1200 rpm or so. I've synched at up to
2000 RPM successfully but most seem to recommend 1200.

6. Peer at manometer tubes/dials - the idea is to get the vacuum equal for
each carb - ie all columns or gauges reading the same.

7. Adjust by turning the carb synch screws on the individual carbs - #4 is
the master and has no adjuster so you have to make the other three line up
with #4 carb.


Adjust in small increments.
Allow the motor plenty of time to settle between adjustments.
Use a light downward pressure on the screwdriver only. Too much opens the
butterfly a fraction and upsets the adjustment.
A mini maglite focused on the adjusting screw aids finding it!
When you have a good balance, swap the manometer tubes to different carbs
and take another look just to check that you don't have a sticky tube or
dial (doesn't apply to mercury tubes)
If using mercury filled manometer take care that mercury is not sucked into
the carb. I've not experienced this but another liSTer mentioned it.

Oh yeah: Check plugs/gaps are in good order and air filter is clean
before doing any of the above.

Contributed by:

Kerry M. Walsh. STOC 116, Pan Clan 338, Paneuro 001
STarduST - Gloucester, England

« Last Edit: December 30, 2007, 05:18:56 PM by KoTAOW »