problems with TB synch

[arek]

I am having difficulty balancing the TBs, where I cannot get them synchronized at both idle (1100) and 2-3k RPM. I can balance them with closed air bypass screws at 2.5k, but as soon as I ease off the throttle one side sucks a lot more air, and opening bypass screws does not help. On the other hand, I can balance the TBs at idle with open bypass screws, but then the balance goes way off opening the throttle ... what gives? Any ideas? I set the valves to world spec, rubber intake boots are good, I do have pods and they are the same. A.

[Kiwi_Roy]

I am having difficulty balancing the TBs

I may not be the best person to respond to this but here's what I did

I balanced them as close as possible with the bypass screws closed using the left and right idle stops.

Then I opened the bypass screws and fine balanced

I balanced at high revs using the white knob on the linkage

Some advocate only using one throttle stop, the left I think but in my humble opinion there's too much slop in the linkage, you want the bike to idle nicely so if you use both stops it will always come back to the same fixed point.

Are you using 2 gauges or a manometer?

Roy

[raz]

Some advocate only using one throttle stop, the left I think but in my humble opinion there's too much slop in the linkage

The rationale is this: If you only use the LH idle screw, the slop is not an issue because it will always be spring loaded. Doing it your way makes this slop affect things off idle. No big deal though, if you get a good result, you're fine!

 

Basically, I

1. set both bleeders half a turn open
2. balance at revs using white knob
3. balance at idle using bleeders
4. repeat and check

When I adjust bleeders, I choose the one that will affect idle speed better: Eg. if left side needs more air for the balance and idle is a tad high, I will close the RH instead of opening the LH.

[Kiwi_Roy]

Basically, I

1. set both bleeders half a turn open
2. balance at revs using white knob
3. balance at idle using bleeders
4. repeat and check

When I adjust bleeders, I choose the one that will affect idle speed better: Eg. if left side needs more air for the balance and idle is a tad high, I will close the RH instead of opening the LH.

That makes perfect sense to me, I have been thinking it might be best to do the high rev balance under load reading the DP while riding either with an electronic DP gauge or something simpler, what do you think?

[fotoguzzi]

did you set your valves first?

[raz]

That makes perfect sense to me, I have been thinking it might be best to do the high rev balance under load reading the DP while riding either with an electronic DP gauge or something simpler, what do you think?

Definitely, but I haven't tried it. I use a "Carbtune II" and it must hang vertically so I can't use it while riding. The difference it would make is probably totally academic anyway, but that doesn't normally stop me

 

did you set your valves first?

Good point

[arek]

did you set your valves first?

 

Yes, I did - 15 in and 20 out. I am going to try again tonight and see if I can get this right. I have balanced TBs few times before, and I did not come across this problem - that is why I posted this. I thought that maybe there is an air leak somewhere, but when I checked everything I could not find one. For balancing I use a self made manometer, which is better than the TwinMax I also have ...