TB imbalance problem and excellent Twinmax

[R1150RDave]

I have completed the service with new spark plugs, adjusted the valves, and checked the tube clips for tightness.
Next, connect Twinmax to the throttles and mount the TM onto the tank so I can observe the balance while driving at speed.
At idle the TB are perfect in sync, at any contant speed the TBs are perfect.

What I noticed when I either throttle off or throtthe on the Twinmax swings to 1 or 2 to the left cylinder for about half second. This happens only with a normal progressive twistgrip action, but if I wack open the throttles the twinmax stays put in the middle.

Vacuum is a result of air and fuel, the latter we cant control with fuel injection. If I suspect injectors I would see the

The Twinmax is measuring vacuum, so is there a problem on the left or right and what could the problem be?

[taosports]

Dave :

Check out this excellent and very humorous tutorial on throttle body synching with the TwinMax. Page 16 may answer your question :

http://advwisdom.hogranch.com/Wisdom/TBS4Dv1.0.pdf

[R1150RDave]

The above article is excellant. I had read this before which was very useful to me having never balance the BM type of carbs/TB.

The responses 1,2 and 3 on page 16 do not fit what I saw on the Twinmax.
When I open the throttle the indicator swings to the left momenterily, then when I close the throttle it swings to the same direction as opening the throttle.
I am happy that the balance will be ok for 95% of driving conditions, but you know what were are like, we strive for 100%

[jm1515]

The above article is excellant. I had read this before which was very useful to me having never balance the BM type of carbs/TB.

The responses 1,2 and 3 on page 16 do not fit what I saw on the Twinmax.
When I open the throttle the indicator swings to the left momenterily, then when I close the throttle it swings to the same direction as opening the throttle.
I am happy that the balance will be ok for 95% of driving conditions, but you know what were are like, we strive for 100%

From all that I've read on TB syncs,
I think your right TB is not coming of the idle stop at exactly the same time as the left on 'gentle' roll on. The right side cable may be just slightly looser (stretched) than the left side, allowing the left side to come of the idle stop microscopically sooner when rolling the throttle and letting the ride side snap back sooner when you throttle down. OR...
The right side idle stop screw has moved somehow (not as likely), same result as above. OR...
The right side cable is binding & needs a dash of lube....

No big deal for now, but what you want is for both TBs to be at their stops at the same time...same 'tension', thus effective length, on the cables.
I would not stress too much, but I might try a slight tightening of the right cable above the bell crank.

[CycleRob]

R1150RDave,
The lack of equality you are seeing is due to wear in the pivot points on the TB throttle shaft bearings and throttle cable splitter spool. It happens normally with high mileage bikes or lower mileage bikes ridden in dirty environments and/or old~damaged air filters. It's not a big deal as you prolly had the sensitivity on high and are seeing miniscule changes as big errors. What you observed is common. The synch is set for the steady state throttle, so those deviations play themselves out before you "take a reading".

[R1150RDave]

Thanks for your replies, checking the cables I found a broken wire on right side throttle, tho not stopping the function of the throttles I see how it may give the symptoms when seen with the Twinmax on highest sencitivity.
If the problem is due to worn/leaking throttle spindle, would a spot of oil dropped into the bearing stop the symptom long enough to prove that was the problem?