FJR1300 Throttle Body Synchronization
600 mile service for the FJR1300
calls for an EFI (electronic fuel injection) "throttle body
synchronization". At every
4,000 mile service after that the
idle speed and throttle body
syncronization should be checked, and adjusted if necessary.
I do most of the servicing of my bike myself, as I am moderately
comfortable with mechanical stuff, and want to be sure it gets done right.
I bought the official Yamaha FJR1300 SERVICE MANUAL to guide me.
I have now done this procedure multiple times. The work you have to do
to prep for this is almost identical to what you have to do to
change the spark plugs,
so you might want to combine the two service items.
Initially, I borrowed one of the
carb sync'ing tools so highly
regarded by oil-head BMW owners. Unfortunately, I didn't have much luck
with it and had to give up.
Some folks favor the
Morgan Carbtune II, from the U.K.,
but I bought the tool that my favorite
motorcycle shop uses, namely, a Motion Pro
tuner, for $35. It worked great!
The Motion-Pro carb tuner looks like this. I hang it on a step ladder
which I park close to the handlebar, or use this simple
front-end stand. The only tricky part was
figuring out where it hooked up, and what to adjust. The shop manual
provided the answer.
Oh, by the way, the various brass adapters provided with the Motion-Pro kit
aren't needed to do the sync on the FJR1300. The plastic hoses fit
directly on the throttle body nozzles.
It described how to raise the front of the gastank, which I'd already done
previously when mounting a power outlet. It also specified removing the
"T-bar" which I found was an unnecessary step, so I left it attached.
I blocked up the front of the tank with a 9" scrap of plywood.
This works fine if your tank is fairly full, but if it is quite low (one
bar showing) you won't be able to get the engine to run.
Yamaha numbers the cylinders left (#1) to right (#4) from the
perspective of sitting on the bike in the riding position.
Thus the #4 cylinder is on the end of the engine nearest the cam chain
You have to remove 4 small rubber caps, each with a small wire retaining
clip. Be extra careful removing these, as they are very easy to
lose. I used a small pair of ignition pliers to do the job.
A trick I used the 2nd time I did this was to string a bit of safety wire
through the small wire retaining clip as shown in the photo above. I left
the wire on until I was all done an put the rubber caps back on.
one cap on the top of each throttle body -- the green arrow in the photo
below shows the location of the cap on the #3 throttle body (its barely
visible behind the gray plastic electrical connector).
is the right side of the engine, where the #4 cylinder
is (you're supposed to use the #3 cylinder as the baseline).
Each of the 4 vacuum lines attach to a small brass nipple (which you can
see better in the photo below).
The upper red arrow points to vacuum line
#4 from the Motion-Pro tool, the lower red arrow
identifies the screwdriver inserted into the #4 cylinder's air screw
used to make the adjustment.
The photo above shows the left side of the engine.
The arrows show the vacuum line
attached to the #1 cylinder's nipple, with the screwdriver in the #1
cylinder's air screw.
The vacuum line plugs directly onto the nipple, the Motion-Pro adapters
The way things are laid out, the #1 and #2 air screws point to the left
side of the engine, and the #3 and #4 air screws point to the right side,
which makes it fairly easy to reach them with a long narrow-bladed
The syncronization itself is almost trivial. First, warm up the engine for
a few minutes (I waited until 2 bars showed on the temp guage), then hook
up the carb sync'ing tool and check the levels. Mine were out of balance,
but not horribly so. I just adjusted the #1, #2 and #4 screws so their
levels matched that of the #3 cylinder. That's it!
The left photo above shows how far the throttle bodies were out of sync at
the 8,000 mile service. At the 600 mile service they were much further out
of sync. The photo on the right above shows how close they were after I
was done sync'ing them. BTW -- the Yamaha spec calls for them being within
10mm of one another
(one of the black horizontal lines on the guage in the above photos is 10mm).
By that measure, my throttle bodies probably didn't need sync'ing.
It probably took me a minute or less to get the throttle bodies sync'd,
with about 15 minutes on each end to gather and put away the tools, read
the directions, disassemble and reassemble the parts, etc.
Another use for the 9" scrap of plywood is to push the rear edge of the
gastank forward so as to get the two retaining bolt holes at the top of the
tank near the steering stem to line up properly.
The official directions, per the FJR1300 SERVICE MANUAL
Prior to synchronizing the throttle bodies, the valve clearance and the
engine idling speed should be properly adjusted and the ignition timing
should be checked.
(I checked the idle speed, but assumed the valves and
ignition timing were OK)
The specs say that the vacuum pressure at engine idling speed should be
33.3 kPa (250mm Hg, 9.8" Hg). The Motion-Pro
tool is calibrated in cm Hg, but the marks are off by about 1 cm
(I used a ruler to verify this). I made sure my #3 cylinder was right at
the recommended 250mm Hg.
The max. difference in vacuum pressure between two
throttle bodies should be 1.33 kPa (10 mm Hg, 0.39" Hg).
- Stand the motorcycle on a level surface.
(I put mine on the centerstand)
- Remove the rider's seat, the fuel tank, and the T-bar.
(I simply raised the front of the gastank and blocked
it up with a 10" piece of 2x4, and left the T-bar in place)
- Remove the 4 rubber caps.
(I warmed my engine up prior to this step)
- Install the carb sync tool. Install an inductive tachometer
onto the spark plug lead of cylinder #1.
(I relied on the dash-mounted tachometer instead)
- Install the fuel tank.
(I never removed mine so I skipped this step)
- Start the engine and let it warm up for several minutes.
(My engine was still properly warm at this point)
- Measure engine idling speed (should be 1,100 to 1,000rpm) and
adjust if necessary.
(Mine was within spec)
- Adjust the throttle body synchronization. After adjusting each
throttle body, rev the engine 2 or 3 times, each time for less than
a second, and check the synchronization again.
- Recheck engine idling speed, and adjust if necessary.
(Mine was still fine)
- Stop the engine and remove the measuring equipment.
- Reattach the rubber caps and retaining clips, reattach the gas tank,
and resinstall the seat.
Copyright © 2002, by H. Marc Lewis. All rights reserved.