Throttle body balancing... need advise as someone has been messing !

beaver

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Think someone has twiddled my bits... could not work out why one pot started higher on vac but was overtaken by the other as it went off tickover... but guessing someone has twiddles the min setting / tickover screw.
The one on the other side has blue paint on it and it’s been moved from factory set... any ideas on how to re-set them for base idle????
Its the one right at the back in the middle of this pic...

I’m guessing you take all cable tension out and set with vac gauges somehow.. but do I disconnect the anything?.. .. carbs are so much easier LOL...
 

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You will need to disconnect the stepper motors or use a gs911 to park them. Then see if you can balance the bodies from tickover to around 3k should suffice.
 
No... I didn't know I had stepper motors LOL...how do you lock them out?.. think both sides have been moved.. should one be a datum to set the other to... all that said.. the bike idles very well and does not surge... does all this refer back to a fuel pot also?.. or it that old school??.. :)

I'm guessing the thing on the RHS is the stepper motor... so assume its for cold running (if I relate to cars)... so do you just disconnect it?... when warm or cold?
 
If you don't have a GS911 then I think I am correct in saying you need to disconnect them before balancing the throttle bodies. I stand corrected if that is duff advice!
 
No... I didn't know I had stepper motors LOL...how do you lock them out?.. think both sides have been moved.. should one be a datum to set the other to... all that said.. the bike idles very well and does not surge... does all this refer back to a fuel pot also?.. or it that old school??.. :)

I'm guessing the thing on the RHS is the stepper motor... so assume its for cold running (if I relate to cars)... so do you just disconnect it?... when warm or cold?
Both throttle bodies have an idle control stepper motor,
In order to balance the throttles they have to be parked/locked in a set position.
This can be done using a gs911 or by disconnecting the electrical connectors.
Ensure valve clearances and all other service adjustments are good.
Engine up to temp
Turn ign on without starting,give it a moment to park the motors,
Turn ign off.then disconnect the motors on both sides.
Carry out balance with vac gauges.
Don’t be surprised if the readings vary a bit ,unless they are a mile out don’t be tempted to adjust base settings.
Adjust cables to get the readings in balance as you open the throttles a tiny bit.but ensure you have 1mm ish of free play in both cables
If they are out ,you will hear the engine going lumpy as the start to open the butterflies.
When you are happy with it,turn off and reconnect the motors.
IGN on without start,wind throttle from closed to fully open 3/4 times ,this should reset motors.
However,it really is better to use a diagnostic tool,we have had a few twin cams that freaked out after balancing,the revs would surge from idle to 3k and the only thing that sorts them is to do a full adaptation reset ,which can only be done with the diag kit.
 
I'm used to the 14cux Lucas system, where you block off the air bypass to set the base idle, . you set it to about 600 rpm then let the stepper do its job when re-connected... guess its a similar thing, but your also balancing two bodys at the same time... is it closed loope / open loop system?...

Can I not balance the system at high RPM and then let it drop and balance at low??.. :)



CRoss posting... Thanks MIke.. will follow that and see if we can get them set.... did you say what the RPM should be from the screw settings before the steppers take over?.. .. but I think the base settings are messed with as vac gauge on tickover is out?.. cheers
 
Mine balanced fine by disconnecting the idle stepper motors but the engines is awkward to start as it won’t run below 1500 rpm and there is no idle control.
I used an electronic differential pressure gage that let me get them pretty well bang on. I was able to ride the bike with gauge connected but balance remained the same all the way up. Expected TBH any range error would suggest a throttle cable is stretching or some other weird thing going on. Engine revs are irrelevant as an unloaded engine hardly uses any more throttle to go flat out than it does at tickover.

When done, stop engine switch off and reconnect idle steppers.
Then can only be balanced with the GS911 or whatever tool you are using. But they can stick or otherwise not be ideal. The only way to know is via a GS911.

I noticed the engine was smoother on initial clutch take up and moving off. But once at speed, I could feel no power difference and vibration was unchanged.
 
I would align the paint marks of the screw again if possible and then repaint it to seal it. Leave it set once done. I dont know if they are set up on an airflow bench or just by a clearance at the factory.

You aren't ever meant to adjust the factory setting of the idle, just the throttle plate position. Whoever has been tweaking your bike in the past has been doing it wrong.

Best method is to use a GS911 to recalibrate the zero setting of the idle steppers, then park the idle steppers and adjust throttle balance (this guarantees they cannot interfere with idle balance). Finally resinstate and re-zero the idle steppers.

I presume the fuel injector is disconnected just to reveal the screw in the picture ?
 
yes.. just wondered if there was a gap to set them to.. .005" or something on the butterfly as a zero point? The paint has almost gone on the screws...
 
yes.. just wondered if there was a gap to set them to.. .005" or something on the butterfly as a zero point? The paint has almost gone on the screws...

I guess if all else fails you can remove the opposite throttle body (assuming it has never been tweaked also) and look at the gap ? Maybe get a feeler gauge in there ??
 
paint gone on both...

Also, is there a pot to re-set??
 
as per above... does anyone know the volts in the closed position???? :)
 
as per above... does anyone know the volts in the closed position???? :)

Not a clue. But the steppers do park themselves when engine is switched off. So I’m not sure closed position has any useful value. The only way to measure voltages would be with patch leads and much faffing about.
 
No.. there is a throttle pot that tells the ECU the throttle position... the throttle needs to be set at a given gap / flow when closed, but also in this position, the pot needs to be adjusted to give the correct volts to the ECU... so there must be a 'at rest' voltage setting.....

Mmmm.. just looking on line.. I can get a pre-used 2010 set with 10K on them for £100... may be worth going this way assuming they are set on the screws and pot, they should be plug and play...
 
Mine runs smoothly (as smooth as any SC Hexhead) but its not ticked over smoothly for a very long time. I suspect a stepper is sticking.

This check might be worth doing

 
Mine runs smoothly (as smooth as any SC Hexhead) but its not ticked over smoothly for a very long time. I suspect a stepper is sticking.

This check might be worth doing


Not sure what that vid has to do with anything... anyway, to save time as it appears the answer is not out there, I've ordered a used set with 10K miles on them, blue paint in tact and pot set... should be plug and play... but will take a measurement so I can set mine up correctly and may be re-sell on...
Result... THanks for all your suggestions anyways..., :)
 
No.. there is a throttle pot that tells the ECU the throttle position... the throttle needs to be set at a given gap / flow when closed, but also in this position, the pot needs to be adjusted to give the correct volts to the ECU... so there must be a 'at rest' voltage setting.....

Mmmm.. just looking on line.. I can get a pre-used 2010 set with 10K on them for £100... may be worth going this way assuming they are set on the screws and pot, they should be plug and play...

Throttle potentiometer on a 1200 is fixed and non adjustable
 
is it?.. on that basis, is I can find out the 'at rest' voltage, I can set the gap....
 
Not sure what that vid has to do with anything... anyway, to save time as it appears the answer is not out there, I've ordered a used set with 10K miles on them, blue paint in tact and pot set... should be plug and play... but will take a measurement so I can set mine up correctly and may be re-sell on...
Result... THanks for all your suggestions anyways..., :)

Vid shows how to test the stepper motors. If both sides are doing the same then we can assume both are working correctly.
 


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