1200 hexhead throttle body balance

[GB.]

Got a bit of an anomaly with doing this. Here are the symptoms; if I get the idle balanced correctly it's out everywhere else in the rev range. Now I have done it by the book, correct temperature turned off the idle stepper etc with the GS911 Now it runs better at high rpm with no real difference at idle, but I know it's not right, where am I going wrong?

 

[Beemerman59]

Have you recalibrated the idle steppers with the GS911? I tend to look for balance at 3K revs, whether thats right or wrong I don't know but feels OK to me.

 

[GB.]

Yes I have and that's what I don't understand, I reset them twice, once before and once after and my gauge ( old fashioned water tubes) it still shows it out at idle?

 

[Bendy toy]

I did mine with a Twinmax connected while I drove the bike. The steppers only come in at low revs, so this gave a real world balance setting. I did not adjust the steppers, but the bike picks up and idles smoothly so that will do until I get GS-911.

 

[Beemerman59]

Have a look at the rubber bung thingies that fit over the vacume take offs on the throttle body - make sure one isn't damaged or cracked.

 

[GB.]

Done that too, gonna try using the GS 911 to test the injectors and O2 sensors. There is an issue with the twincam models needing a reset all adaptations values after an idle calibration but mines a pre twin cam but I could try that.

 

[Magwych]

Are you sure no-one has been adjusting the stop on the right-hand side?
I had similar issues, then, when I had the RHS throttle body off (for other reasons) I noticed that the butterfly closed completely, and the stop on the cam did not even touch the screw. I recall that a long time ago it came back from a service "not quite right" and I had to reset the cables to get equal vaccuum off idle but I have never got equality at idle.
I have just taken the plunge, carefully set valve clearances, new plugs and using my TwinMax alike gauges adjusted the right stop to bring the pressure into line at idle. Steppers parked using the GS911. I know that these are normally factory set and should not be adjusted, but someone clearly had so I felt I had little to lose.
Idle and just-off-idle are so much smoother now, no spitting back on the right or exhaust popping on gear change.
I am not saying you should this, or approach it lightly, but it is possible some helpful minded technician "had a go" at the stop.

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[GB.]

When you say stop, what exactly do you mean, the stop for the cable itself?

 

[(RIP) Bin Ridin]

When you say stop, what exactly do you mean, the stop for the cable itself?

The stop screw for the butterfly shaft cable pulley.

 

[Magwych]

No, I meant the stop for the cam quadrant that the csble connrcts to. At rest there should be slack in the cable because the quadrant is resting on the stop screw. It is underneath the domed plastic cap in front if the cable adjuster on each throttle body. It controls the position of the butterfly valve when the cable is slack, i.e at idle. Do not play with this unless you ae confident about it. You may be able get a good dealership to check it for you, if you have good reason to believe it has been moved. On mine that plastic ant-tamper cover had been removed and not refitted, that was my first clue. Seeing that the quadrant did not even touch the screw at idle was my next

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[Popell]

Ditto on the idle imbalance - just balanced at around 3k so achieving smooth running at real speeds.
No access to GS-911

 

[GB.]

Rode it home last night and it is much smoother at speed and I can't notice a lot of difference at idle, will look at it again the weekend