Balancing throttle bodies

I’ve just given my big Breva it’s annual fettling. The instructions for balancing the throttle bodies say to close both air bleed screws, balance the throttles via the link rod while at 3000rpm and then return to idle. Any difference in the readings at idle should then be taken out by opening one bleed screw. But, this last action affects the balance at higher rpm. Is it not more important to get the balance right at normal running speeds rather than idle?

I’ve recently done the very same for the first time. Followed the instructions as you have and the seat of the pants feel test riding the bike afterwards confirmed the bike felt better than before the balance was done.I didn’t bother looking at the balance after setting the idle by opening the bleed screw though, so if it affected the throttle balance it was negligible I suggest.

You’re on the right track.

This is what I do on both my bikes, but the principle works on any bike (twins, obviously).

First, take the bike for a ride to get it warmed up thoroughly. Idling for 10-15 min won’t do it and air cooled engines don’t like it.

Close the air bleed screws. Adjust engine speed to approx 3K. Balance cylinders using rod adjustment (or linkage on other bikes). Then return engine to correct idle speed. Back out air bleed screws approx 1 turn and check balance at idle. If incorrect, adjust using the screw on ONE cylinder only until correct. You may need to re-adjust the idle spped a little at this point. Job Done!

On checking, you might notice a very slight imbalance on very light throttle openings at higher revs (I never have), but the air flow through the throttle bodies will very soon exceed the air bypoass screws and you’d never notice in reality. When you rev the engine, the revs should rise and fall together and not lag behind each other at all. If they do, it’s out somewhere and it’s a case of restart the process.

Hope this helps.


Hi Mark - pretty much as above on my 1100 sporti but I >always< check the valves and inlet rubbers first.
p.s. Going to the Scottish this year? Afraid I can’t due to work committments.

Please note that after adjusting the balance it is imperative on the Breva that the TPS setting is reset. It is also not possible to adjust idle speed without breaking the warranty conditions.
The new 15M ECU is very different to earlier models.

The very reason I hadn’t tried it 'til now. I hadn’t discovered Ducatidiag until recently

A good bit of software that, just wish it had come out before I forked out all that money on the Technoresearch VDSTS.

Surely the TPS setting won’t need to be adjusted unless incorrect. After all, it’s function is to measure the amount of throttle opening and relay that info to the ecu. Adjusting the balance would not change the relative position of the throttle butterfly and the sensor as you’re adjusting the linkage between the two throttle bodies. That said, it’s never a bad idea to check to make sure it’s accurate. I know from experience that a small deviation from optimum can make a marked difference to the performance.

I wasn’t aware that adjusting the idle speed would invalidate the warranty. I’ve not heard of that one before.

Ill just be smug with a MyECU.

I have left all my settings well alone as it seems to run ok
but I was not aware that you could adjust the settings without diagnostic equipment in case you upset the catalytic convertor
it all sounds to complex for me and I would be afraid of messing it up
also being familiar with the operating system is a must quite beyond me I am afraid, i use some high tech kit as a sparkie but have met peopel who have purchased it for DIY soem have done ok but quite a few have been chasiing loose ends and wasting time
I think I will pay soem oen else to do it, I am surprised no one does mobile tuning like the old hometune

rapheal glynn2012-04-22 11:52:23

Thanks for all the advice. I am still at a loss as to why the balance at 3000rpm should alter when I opened one bleed screw. As Trevini said, the amount of air passing the air bleed screw should be insignificant at higher revs. I had Ducatidiag plugged in during the whole process. The TPS didn’t need adjusting and the reading did not alter during balancing. Valve clearances etc were adjusted beforehand.
Gavin, I did have the airbox off to replace a dodgy oil pressure switch so I will have to double check for air leaks and then check everything again. No Scottish for me either this year, family commitments, I will never forget that run through Wester Ross last year though, great weather and great company!

Keep one bleed screw closed at all times adjust the tickover balance with the screw that has the highest reading on the gauges.

Balance the throttle bodies at approx 3000rpm if you do need to adjust the linkage rod the TPS will need to be reset - dead easy with ducatidiag.
Recheck tickover balance again if required and repeat until both cylinders are balanced, not too difficult. Last job reset TPS as mentioned with throttle closed, engine off and ignition on.

The engine will get too hot if you take your time so a good fan to blow cool air from the front is a good idea.

TPS on Breva 1100 = 4.6 Tickover 1100rpm.

The TPS is mounted on the RH throttle body, the cable on the left one, so any adjustment of the linkage to balance them will affect the TPS setting.
Remember we are talking about the Breva/Norge etc models here. There is a throttle stop screw on these, but it is factory set and according to Guzzi, if any adjustment is made to that screw, which is sealed with yellow paint, it will invalidate the warranty on the TBs.

My only advice on this is balance the throttle bodies to your riding style.
IE if you ride a 3k all the time, balance at get a far better ride and the engine feels sweeter

I’m sorry, but your statement above, “The TPS is mounted on the RH throttle body, the cable on the left one, so any adjustment of the linkage to balance them will affect the TPS setting”, is incorrect. It will not adjust the setting, only the reading sent to the ecu. The only way to adjust any TPS setting on ANY vehicle, Breva or not, is to move it in relation to the throttle butterfly.

Please don’t take this the wrong way, no offence is intended, but the TPS is set to measure the butterfly angle of the throttle body in relation to the body it’s attached to and NOT any other (that’s achieved by balancing). That reading is more often measured as either a percentage of angle in degrees, although it can also be measured in mv. TPS generally uses 0.5-4.5v, so the idle position will generally be in the region of 500-550mv. A few hundred mv either way can make a marked difference. The reason for not using 0-5v is to allow for the ecu to run a trickle current through the unit for self diagnosis purposes at the lower end to allow for manufacturing tolerances.

Adjusting the throttle stop on a throttle body will not affect the TPS setting. What it will alter is the reading sent to the ecu, which in turn will alter the fueling and ignition timing accordingly. I think your confusion is coming from the distinction between TPS reading and setting. The setting is the position of the sensor in relation to the butterfly. The reading is the output from the sensor telling the ecu how far open/closed the butterfly actually is.

Factory specs dictate the reading should be within a tolerance with throttle closed against the preset throttle stops. They know the TBs were factory set at a predetermined throttle angle (and what it is). The TPS setting to which you refer is the angle or percentage of opening that they specify at that point.

The TPS doesn’t just measure at closed throttle, it’s required at all throttle and rpm conditions. The factory set throttle screw to which you refer is set to a specific throttle angle (measured by a correctly set TPS and not altered by it). To give an example - a throttle butterfly is “actually” open at 3% and the TPS gives a reading that corresponds accurately to reflect this, either as a percentage or angle. By altering the throttle screw does this alter the throttle position or adjust the TPS? The answer is that it alters the throttle position. In order to set the throttle screw at the correct setting, an accurate TPS reading must be obtained. Logically, there are only three throttle positions that can possibly be accurate to achieve this because in order to calibrate the setting - either fully open (100%)or fully closed (0%). Fully open is easy to achieve, twist the throttle and look into the throttle body to ensure it’s fully open. Fully closed means backing off throttle stop screws and losing factory base settings, so less than ideal. The third is the preset factory setting, set by the throttle stop screws. Bottom line is that you’re stuck with the factory default throttle stop settings that shouldn’t be altered. Most vehicles have the “screw that shouldn’t be touched”,but can you guarantee that the throttle stop screw set in the factory and daubed with yellow paint is accurate? No. Factory set, yes it is (on most bikes and cars, not just Guzzi) As for invalidating the warranty on the TBs, The original bike in question is an 1100 Breva, long out of warranty by now, unless the warranty on the TBs is greater than the original factory warranty.

There is no doubt that the factory will specify a range within which the throttle body has to be open, measured by the TPS. This is due to a number of reasons.

Firstly, ignition timing and fueling will be more or less correct to maintain a stable idle, with fine adjustment being available through air bypass screws to adjust idle speed along with electronically adjusted CO to correct the mixture.

Secondly, to provide a base setting for any other throttle bodies/linkage prior to balancing the airflow through them as a set.

Thirdly to allow for manufacturing tolerances in the TPS and TBs themselves (although they are very good).

Where the cable connects is largely irrelevant - with the linkage in place and no cable connected the same TPS readings will be given.

Having re read my original post several above this one, I didn’t make it particularly clear. I didn’t actually say alter the throttle stop screws, only the air bypass screws. “Adjust engine speed to 300rpm” is achieved by twisting the throttle. Sorry for the confusion.

As I ststed above, please don’t take offence, none is intended. I’m only trying to help and offer an explanation.


Maybe I should have said altering the linkage length to adjust the balance at higher throttle settings will affect the TPS READING.
This, on the B1100 etc can only be altered or reset with software unlike your V11.

On my Norge, I found the balance at higher throttle settings was out every time I checked it, but a drop of loktite on the linkage adjustment screw worked wonders. It hasn’t altered since.

Yes of course the bike in question is out of warranty, but the warning should still be heeded, as fiddling with such things by someone who is not a fuel injection expert is likely to open a can of worms.
It may be that the stop screw is not set perfectly by the manufacturers, but I guess they have a template to acheive the correct butterfly angle and set the stop to that. How do you prove this is wrong? Seems to me that unless you also have quite sophisticated measuring equipment, you can’t, and certainly 99% of owners couldn’t, so best advice is to leave well alone.
You must also remember that this is a public forum, and advice given here is in the public domain, thus if someone were to follow advice given by individuals here and it all went TU, they could reasonably sue for the cost of putting it right. This is why we do have to be careful.

Absolutely correct advice.


Please note that the only reference I made to any of my own bikes was that the procedure I followed is used commonly by me on both of my own bikes. It seems to be you, Brian, that keeps pointing out the proceedure is different to my V11. Having compared the manuals for both bikes, the balance procedure is very similar between a V11 and B1100 and more or less word for word as I described. They have different specs for the throttle angle for the TPS setting and the set up procedure is different for the TPS on both, as you have correctly pointed out. Everything else I have commented on has been generalised and descriptive of how the systems work. I hope that it was of use to people and maybe even prompted further investigation into the technical sides of FI systems.

The fact that this is a public forum should not, I hope, prevent anyone from having a discussion about any technical subjects (or pretty much anything else for that matter) for fear of being sued. If that is the case, we probably shouldn’t be discussing anything. I should also point out that all I did was question a statement that you made initially in order to seek clarification. If you feel any of my contributions are inaccurate and/or likely to end with the club or it’s members in hot water, please feel free to remove them, or I will at your request. It is, of course up to the individuals to make up their own mind which advice, if any, they want to follow. I can’t copy and paste from any specific manuals, as that would be a breach of copyright without permission to do so, but the information is available to purchase (not from me) relating to specific bike models and general motor vehicle engineering principles. Personally, I think you may be being a bit too jumpy regarding the sueing, perhaps for good reason from an experience, I don’t know. That said, I will, of course abide by the club rules and as I have stated previously, have no intent to cause offence.


No offence taken at any time Trev, and nothing you have said is cause to remove anything.
It’s good to discuss, helps to clarify the detail (in which often lurks the devil ).

Fair play, thanks.

technically its not public this section is for members only so hopefully they take tips in the spirit of learning
I am walsy interested in finding out how it works
but am unlikely to attempt any adjustment myself as I am a conjenital idiot
I can just about manage to check the oil and do the tyre pressurs