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Moto Guzzi Throttle Body Synchronization

Synchronizing the Throttle Bodies on a Moto Guzzi California 15M

This article will focus on synchronizing the Throttle Bodies on a 2000 Moto Guzzi Jackal.  I believe this will apply equally to Bassas, Stones, and any other Moto Guzzi California from 1999 on equipped with the 15M ECU computer.

Synchronizing the Throttle Bodies is an important part of a proper Moto Guzzi tune-up, but is only one part of it.  Before you get to synchronizing the Throttle Bodies, normally you should already have taken care of your motor oil, air filter, spark plugs, and valve clearances.

Also, this should be done before adjusting the Throttle Positioning Sensor (TPS), as TPS relies on a good idle. See the References section at the end for good references on fluid changes and valve adjustment.

I encourage all constructive feedback or questions. Please e-mail me at


  1. Manometer, CarbTune, or TwinMax — these are to measure the vacuum;
  2. A 2.5 mm Allen key;
  3. A few mid-sized flat screwdrivers. You may want a long one with a mid-sized blade (Idle Adjustment Screw), and a short one with a somewhat fatter blade (Air-Bleed Screws); 
  4. Small shop mirror. It is nice when dealing with the air-bleed screws.

Before getting started, there are some things we may as well go ahead and locate on the bike:

1. Throttle Stop Screws: There is a horizontal screw w/ a 2.5 mm Allen on top of each Throttle Body. From the factory, it has yellow paint on the Allen fitting;
2. Idle Adjustment Screw: This is in the center of the motorcycle.  The Choke (or Fast Idle if you prefer to call it such) is connected to this.  It is a plain-Jane slotted hex head;
3. Air-Bleed Screws: Each Throttle Body (TB) has 2 vertical tubes when viewed from the side.  One of them is sealed; the other has a brass slotted screw in it.  I like to use a small shop mirror to see where the screws are set before and after I adjust them;
4. Synchronization Screw: This is on the top of the left Throttle Body.  It is a 7 mm hex head;
5. Vacuum ports: There is a vacuum port on each intake manifold collar, on rear of the jug, between the jug and the Throttle Body.  If you are lucky, you will have a hose connected to it already.  If you are not lucky, like me, you may have a screw in it to cap it off.  If so, you can buy 6 mm brass fittings for them through most mail order shops.  Your local bike shop likely will not carry it for sale, but will have them in the mechanic’s toolbox.



  1. Start with a hot bike turned off. Make sure the bike has been ridden enough to get up to normal operating temperature. Some people say that may take 20 minutes, some say 20 miles.
  2. Close the brass bypass screws on the TB’s.
  3. Connect your balance meter/carb sticks and PC w/ EFI diagnostics software if you have it.
  4. Start the bike. Ignore the fact that it runs worse than it did.
  5. Unscrew the Throttle Stop Screws on each TB (2.5 mm Allen) so the screws do not touch the plates, the plates are against the housing or whatever, and the screws may as well be out of the bike but are still in place, so they have no effect on idling.  You may want to disconnect the Linkage Arm on the left side to get better access to the screw on the left side.  If you do that, be careful when removing the e-clip (or c-clip or whatever you want to call it).  It will want to fly off.  Put some electrical tape behind it to keep it from going into orbit.  Pry it off with 2 small screwdrivers.  It is small, and it will fly off, and it will be hard to find.  If you do disconnect it, once you get the Left Throttle Stop Screw where you want it, put the Linkage back together.
  6. Adjust idle using the Choke Screw (some call it Fast Idle, I call it choke) in the center of the bike.  Idle should be 1060 RPM +/- 50. Use software, tach, or ear to adjust idle RPM. Long flat screwdriver.
  7. Screw in the Throttle Stop Screws so they just touch the plates, but do not alter the idle.
  8. Use Sync Screw on top of Left TPS to synchronize the TB’s at 3000 RPM. You can use the Choke (Fast Idle) to rev to 3000 RPM and hold it there.
  9. Now check synchronization at idle, remember, the Throttle Stop Screws are, up to now, adjusted so they are not a factor on the idle.  Use the Throttle Stop Screws to sync at idle.
  10. Set the bypass screws to the specs.  This is ½ turn for a Jackal w/ its 15M ECU.
  11. Check the balance at just off idle, say at 1500 RPM for those of us w/ a tachometer.
  12. Use the Air-bypass Screws to synchronize at just off idle, 1500 RPM.
  13. Use the Choke Screw in the center to adjust Idle to 1060 RPM +/- 50.
  14. To be thorough, while you are here w/ all the right tools at hand, you may want to check synchronization again.  I think they should be done a second time in this order:a.) Check just above Idle Use Air-Bleed Screws to adjust sync;
    b.) Check at Idle Use Throttle Stop Screws on each TB to adjust sync Ø Check at 3000 RPM Use Sync Screw to adjust sync;
    c.)  Don’t be shy about adjusting the idle RPM again.

    I suggest doing it in this order on the second go-around, because in my opinion, the bike is most concerned with 3000 RPM sync, as that is where I ask it to do most of it’s work.  I am most concerned with Idle sync, as that is where I am paying the closest attention.

  15. The end!  That wraps up the synchronization of the Throttle Bodies. Turn your bike off, disconnect carb sticks, seal up your vacuum ports, and hopefully enjoy a smoother running, more fuel efficient, and maybe even more powerful motorcycle.

Either while synchronizing the Throttle Bodies, or adjusting the Throttle Positioning Sensor (TPS), it is a good idea to adjust the Trim so the exhaust carbon monoxide level is satisfactory.  Trim on motorcycles with 15M ECU’s can only be adjusted with software.  If you have the software connected for this procedure, you may as well at least note where yours is currently set.  I believe the scale goes from -128 to +128.  It also seems you need to save the changed value, turn the bike off, and then turn it back on to make the change effective.

The US specification for Trim is to adjust for 1.9% exhaust CO.  The rest of the world uses a 3-5% setting.  You will need the EFI diagnostic software and a CO meter to do this.  It might be best to go to your Moto Guzzi dealer for this adjustment, assuming he has the diagnostics software and a CO meter.  It seems to me that if 1.9% is the US specification, and 3-5% is for the rest of the world, 3.75% would be a nice place to adjust this to, unless you live in California.

Q: Will or should this procedure differ on a bike that has no charcoal cans? 
A: I have never gotten an answer to this.

Q: Can you suggest a Trim Setting value to use for a stock Jackal, Bassa, et. al. for those of us w/ no access to a CO meter?
A: Everyone says to experiment to find what works best. I hope to get mine in to a shop with the software and a CO meter so I can set my Trim such that my exhaust is at a 3.75% CO level.

Q: Any suggested alterations for a K&N air filter or H-pipe? 
A: I have been told by a few well-respected Guzzi Godfathers: No, but you may need to re-map. Never heard of anyone re-mapping though.

Moto Guzzi National Owner’s Club: Correspondence List (MGCL); Damn near anything Guzzi. Definitely join this list!

MPH Cycles:  A Moto Guzzi Dealer with a great reputation in Houston, TX.  The Technical section of their website lists specifications for many, if not all, Guzzi EFI’s, and has a good tune-up write-up.

Lowside:  This site used to be on, but something changed.  Very good write-up with great photos on valve adjustment, oil changes, and more.

Torque Web:  A well respected list of common torque values for just about every screw on your Moto Guzzi.

Dennis Kirk:  A nice mail order shop to buy generic motorcycle stuff, tires, helmets, 6mm brass fittings for your vacuum ports, etc…  They will match competitor’s prices if you can document them.  There is a 6$ fee for orders under $100.00.  Their next day shipping is no joke. A catalog is yours for the asking.  Phone 800-328-9280

Jackal Parts Manual – Or the parts manual for your bike.  Mine was only about 20 US$.  They are available from most any dealer. They list all your part numbers, and show how practically everything fits together.  The best $20.00 I have spent on my bike.