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Throttle Sync Question - Range of Movement of Butterflies


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2002 R1150R had some excessive vibrations so I checked the valves, replaced the plugs (3923's) then proceeded to do a TB sync. In the course of checking things out I opened throttle all the way and found the left side to be hitting the upper stop while the right side comes to about 1/16 of an inch but does not hit the stop. I can make it hit the stop by pushing with my finger, so it's not stuck.


Is this a problem and will it affect a good sync??


I then did the following:

1) Loosen all the cables and reset them so the

appropriate minimal slack was present then ensured an

even pull at throttle was achieved. Both throttles hit

the idle stop screws properly after resetting.

2) checked both sides again with throttle wide open and

right side still does not hit upper stop.

3) Hooked up the twinmax and noticed the needle would pull

to the right during accel but would zero out around 4k.

4) BBS screws ar set at 7/8 on the right and 3/4 on the



If the range of the throttles is an issue the only solution I can see to make the range equal on both sides is to adjust the right idle stop screw to make up the difference. I guess I should find out if this is a problem first before proceeding. Does adjusting the right

side idle stop mess things up ?



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The stop screw only controls the position of the throttle plate at idle.


That last little bit of throttle opening is more or less meaningless in terms of total air flow at wide open throttle so I wouldn't worry about it.


When doing the throttle syncronization, I like to use the drop on acceleration as a guide to getting the synch right rather than steady state. It better reflects the movement of the throttle plates IMHO. Usually, this will translate to a synch at steady state as well. If not, it would indicate to me that something is different mechanically or electrically between the two cylinders. Might be a slight air leak in one or the other or a difference in valve adjustment/sealing. I don't worry about getting the last 1/4" of mercury precision either and my motors run fine.

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