Thanks for the explanation. As one that is unfamiliar with the linkage and TBS, what you are describing sounds a lot like an old fashioned carb synch, at least when I used to do those I thought I was adjusting the butterflies (actually the slides) so they would all open at the same time. Now I am wondering what actually is being adjusted with a standard TBS?
If that is all you adjust, it sounds like you are balancing the engine at idle and not much else -- what am I missing?
Bingo. I don't think you are missing anything.
The air bleed screws overlap the entire throttle range, but their effect gets less and less as the throttles are opened. They're designed to "trim" the TB's with the idea that the butterflys will stay synced well enough without adjustment. And idle is where any mis-sync is most noticeable, so according to Yamaha, it is the only place you really need to do the adjustment.
Torch, Mark, thanks for the feedback, its nice to know what is really happening with those adjustments. There is a another active thread discussing vibrations above 4,000 rpms which has been one of my complaints about the FJR since I have owned it. I have had several big in-line fours and the FJR is the smoothest at 4,000 rpms and vibrates the most at 5,000 rpms. Several members have reported that they reduced the vibration above 4,000 rpms by synching the butterfiles but if the engine is smooth at 4,000 rpms (under a load) I would think the butterflies would have to be in synch at that point and have a hard time understanding how vibration above those rpms would be caused by the butterflies being out of synch.
I have noted that several members have stated that using a PC with the Wally Smoothness Map did wonders for reducing vibration which would indicate the FJR's high rpm vibration is really the result of FI mapping or inaccurate FI sensors.
FJR's mostly vibrate because they're a big 1300cc inline-four engine in a motorcycle chassis, not because of FI mapping or sensor glitches.
Sorry to hear you won't be at WFO.
[SIZE=12pt]Synchronizing the FJR Throttle Body Linkages[/SIZE]
Adjusting the TB air screws alone does not provide the most effective TB sync because they only compensate for air flow at idle. Most of your riding takes place at higher RPMs. The throttle valves (butterflies) of each throttle body need to be in sync with each other at high (off-idle) RPM.
This procedure is not covered in the factory manual. However this procedure is common and dealers that know what they are doing (and are willing to take the time) perform this adjustment on many multi-cylinder bikes. Having the TB’s in sync at cruising speeds (not just at idle) makes a huge difference in engine smoothness and vibration.
You should not have to adjust the individual throttle stop screws to achieve this. This assumes that the throttle stop screws have not been grossly misadjusted at the factory (guy on the flow bench had one too many bottles of Sapporo the night before) or the lock nuts have come loose.
To get the engine’s intake tracks in sync the four throttle body linkages need to be adjusted. The throttle bodies are linked in pairs. TB’s #1 & #2 are one pair and #3 & #4 are the other pair—finally the two pairs are adjusted together (#1 & #2 and #3 & #4).
This is a simple procedure but does take patience. The image shows TB #1 on the left and the linkage adjustment screws are circled. Here is what I did to get my FJR in sync.
1) Get the engine hot by going for a short ride. When you are at 4200 RPM in 3rd or 4th gear, squeeze you heals against the frame to feel the level of engine vibration. This highly precise measurement will be used later to determine how good a sync job you did.
2) Raise Tank and connect sync tool.
3) Turn all four air adjusting screws in until they are lightly seated.
4) Back each screw out 1 turn
5) You may want to place a large fan in front of the radiator to keep things cool (including you).
6) Start the engine.
7) The TBs will probably be out of sync to some extent but not more than 1 to 4 cm of Hg. The actual vacuum level does not matter. If they are out more than this keep going through these steps—we’ll fix this later in the procedure.
8) REVING THE ENGINE Slowly rev the engine up to around 4000 RPM while watching your sync tool. What you are looking for is even vacuum levels as engine speed increases. If you try to perform to sync the TBs with the engine speed steady (say at 4000 RPM) you will find that the vacuum levels between each TB will never be in sync no matter how many adjustments you make. It is more important for vacuum levels to be even during moderate, smooth, engine acceleration and not at a steady throttle setting.
9) Using the butterfly sync screw between TBs #3 and #4 (Yellow Circle) adjust the vacuum level so #3 and #4 are the same when you accelerate the engine as described in step 8, “REVING THE ENGINE above. This will take several tries. You may not get them exactly even either, but get them as close as you can (usually within 1 cm of Hg.).
10) Now perform the same procedure on TBs #1 and #2 (Green Circle). You may have to rev the engine half a dozen times to get them close.
11) With vacuum levels for TB pairs #1/#2 and #3/#4 matched it’s time to sync the two pairs of TBs together.
12) Rev the engine as described in step 8, REVING THE ENGINE while watching the two pairs of TBs. If they are off by more than 1 cm of Hg., an adjustment is needed.
13) The adjustment screw can only be accessed with the engine off. The screw is located between the two pairs of TBs (Blue Circle with Arrow). (The throttle has to be opened about ¾ of a turn to get a screw driver on the screw). Turn the screw about 1/8 of a turn (either direction) and restart the engine.
14) Check the balance (vacuum level) between the two pairs of TBs. Shut the engine off and readjust as many times as needed. (By now you and your FJR’s cooling system will appreciate the large fan you are using, step 5.)
15) When the two pairs of TBs are even (when you smoothly rev the engine) you are finished with this step.
16) Now let the engine idle. Adjust the idle speed to 1000. The tach on the FJR is very accurate. I checked it against a $500 electronic sync tool that counts the vacuum pulses during the intake stroke of cyl #1 and then generates an RPM signal on the tool.
17) Now it’s time (finally) to adjust the airscrews on each TB. Use cyl #3 as reference and adjust the other cylinders to the same vacuum level as #3. The actual level does not matter (I know, everyone seems to be hung up on how may cm of HG., but it really doesn’t matter as long as idle speed is kept at 1000 RPM.)
18) Make a final idle adjustment (1000 RPM) and you done. If after syncing the TBs with the airscrews you can’t get the idle speed to come down to 1000 rpm, DON’T KEEP BACKING THE IDLE ADJUSTING SCREW OUT. The TB airscrews all need to be turned in ½ turn. Now the idle adjusting screw will allow you to adjust the idle speed to down to 1000 rpm.
19) Go for a ride and check engine vibration at 4200 RPM (Step 1), it should be better than when you started. If it’s worse, you screwed up the adjustment. The amount of improvement really depends on how far out of the sync the TB linkage was before you started. When done correctly most of the vibration you normally feel at 4100/4200 RPM in fourth/fifth gear should be gone—at least it was on my 2005. Good Luck!
[SIZE=12pt]Synchronizing the FJR Throttle Body Linkages[/SIZE]
Adjusting the TB air screws alone does not provide the most effective TB sync because they only compensate for air flow at idle. Most of your riding takes place at higher RPMs. The throttle valves (butterflies) of each throttle body need to be in sync with each other at high (off-idle) RPM.
This procedure is not covered in the factory manual. However this procedure is common and dealers that know what they are doing (and are willing to take the time) perform this adjustment on many multi-cylinder bikes. Having the TB’s in sync at cruising speeds (not just at idle) makes a huge difference in engine smoothness and vibration.
You should not have to adjust the individual throttle stop screws to achieve this. This assumes that the throttle stop screws have not been grossly misadjusted at the factory (guy on the flow bench had one too many bottles of Sapporo the night before) or the lock nuts have come loose.
To get the engine’s intake tracks in sync the four throttle body linkages need to be adjusted. The throttle bodies are linked in pairs. TB’s #1 & #2 are one pair and #3 & #4 are the other pair—finally the two pairs are adjusted together (#1 & #2 and #3 & #4).
This is a simple procedure but does take patience. The image shows TB #1 on the left and the linkage adjustment screws are circled. Here is what I did to get my FJR in sync.
1) Get the engine hot by going for a short ride. When you are at 4200 RPM in 3rd or 4th gear, squeeze you heals against the frame to feel the level of engine vibration. This highly precise measurement will be used later to determine how good a sync job you did.
2) Raise Tank and connect sync tool.
3) Turn all four air adjusting screws in until they are lightly seated.
4) Back each screw out 1 turn
5) You may want to place a large fan in front of the radiator to keep things cool (including you).
6) Start the engine.
7) The TBs will probably be out of sync to some extent but not more than 1 to 4 cm of Hg. The actual vacuum level does not matter. If they are out more than this keep going through these steps—we’ll fix this later in the procedure.
8) REVING THE ENGINE Slowly rev the engine up to around 4000 RPM while watching your sync tool. What you are looking for is even vacuum levels as engine speed increases. If you try to perform to sync the TBs with the engine speed steady (say at 4000 RPM) you will find that the vacuum levels between each TB will never be in sync no matter how many adjustments you make. It is more important for vacuum levels to be even during moderate, smooth, engine acceleration and not at a steady throttle setting.
9) Using the butterfly sync screw between TBs #3 and #4 (Yellow Circle) adjust the vacuum level so #3 and #4 are the same when you accelerate the engine as described in step 8, “REVING THE ENGINE above. This will take several tries. You may not get them exactly even either, but get them as close as you can (usually within 1 cm of Hg.).
10) Now perform the same procedure on TBs #1 and #2 (Green Circle). You may have to rev the engine half a dozen times to get them close.
11) With vacuum levels for TB pairs #1/#2 and #3/#4 matched it’s time to sync the two pairs of TBs together.
12) Rev the engine as described in step 8, REVING THE ENGINE while watching the two pairs of TBs. If they are off by more than 1 cm of Hg., an adjustment is needed.
13) The adjustment screw can only be accessed with the engine off. The screw is located between the two pairs of TBs (Blue Circle with Arrow). (The throttle has to be opened about ¾ of a turn to get a screw driver on the screw). Turn the screw about 1/8 of a turn (either direction) and restart the engine.
14) Check the balance (vacuum level) between the two pairs of TBs. Shut the engine off and readjust as many times as needed. (By now you and your FJR’s cooling system will appreciate the large fan you are using, step 5.)
15) When the two pairs of TBs are even (when you smoothly rev the engine) you are finished with this step.
16) Now let the engine idle. Adjust the idle speed to 1000. The tach on the FJR is very accurate. I checked it against a $500 electronic sync tool that counts the vacuum pulses during the intake stroke of cyl #1 and then generates an RPM signal on the tool.
17) Now it’s time (finally) to adjust the airscrews on each TB. Use cyl #3 as reference and adjust the other cylinders to the same vacuum level as #3. The actual level does not matter (I know, everyone seems to be hung up on how may cm of HG., but it really doesn’t matter as long as idle speed is kept at 1000 RPM.)
18) Make a final idle adjustment (1000 RPM) and you done. If after syncing the TBs with the airscrews you can’t get the idle speed to come down to 1000 rpm, DON’T KEEP BACKING THE IDLE ADJUSTING SCREW OUT. The TB airscrews all need to be turned in ½ turn. Now the idle adjusting screw will allow you to adjust the idle speed to down to 1000 rpm.
19) Go for a ride and check engine vibration at 4200 RPM (Step 1), it should be better than when you started. If it’s worse, you screwed up the adjustment. The amount of improvement really depends on how far out of the sync the TB linkage was before you started. When done correctly most of the vibration you normally feel at 4100/4200 RPM in fourth/fifth gear should be gone—at least it was on my 2005. Good Luck!
