Synching Throttle Bodies

[TJR178]

Ok, so I'm having issues with a rough idle.  My bike idles around 800-900 but then drops until it almost stalls (and sometimes does).  I'm being told I need to synch my throttle bodies.  Is this something I can do?

Suggestions?

[battlecry]

I'd raise the idle 300-400 rpms first and see if it smooths out.

[scott_araujo]

+1.  The recommended idle speed for your bike is probably printed on the sticker under the seat if it's still there.  It's usually around 1200RPM.

Scott

[TJR178]

I should've said that I've raised the idle (with the lever), but it still seems to happen from time to time, though not as bad.  I usually have it idling at least 1500 rpm.

[scott_araujo]

I'd say that without the right idle speed without the lever you don't have much to go on.  I'd recommend that you do a TPS reset, set the idle speed, set the idle CO, and synch the throttle bodies.  If you have a newer bike you'll need a computer hookup for the TPS resest and idle CO set.  You need to be able to do those to set the idle speed and then the last step is the TB synch.  You can do the synch with a homemade manometer but I think you need more than that to sort out your current issues.

Scott

[DucHead]

^^  yep, but you have a non-linear TPS.  Brad Black did a write up.

Here's the synopsis (edited for my bike -- I, e.g. I removed the fast idle assembly):
1. Disconnect the throttle cable at the throttle cable wheel (9).  Easiest to just take the cable out of the wheel rather than play with the adjuster.
2. Disconnect the throttle linkage rod (6).  You can pop off the plastic connector on the horizontal throttle body, or you can wind out the throttle linkage adjustment nut (11) to make sure the vertical throttle butterfly is open more than the horizontal throttle butterfly.
3. Connect to the TPS by whichever method you are using to measure the TPS output voltage.  Turn on ignition.
4. With the throttle closed before you start you should be seeing voltage in the range of 300 â€" 450 mV.  I usually record this voltage, just in case I need to go back to it.  
5. Back off the horizontal cylinder idle stop screw (7) to allow the throttle butterfly to close fully and jam if snapped or pushed.  
6. Open and close the horizontal throttle butterfly gently until the voltage stabilizes at a minimum.  Do not snap the throttle butterfly shut.  The voltage will be in the range of 90 to 170mV.  Record this voltage out of suspicion.
7. Reset the TPS to give an output voltage of 150 mV by loosening the two screws (2) and rotating the TPS.  Tighten the two screws (2) and ensure the setting remains consistent.
8. Wind in the horizontal throttle body stop screw (7) until the TPS output voltage is at the required idle setting for your model (Desmoquattro S4R: 423 mV; 2.6°).  
9. Open and close the throttle a few times to check the idle setting is stable and adjust if required.  The TPS is now set and the horizontal throttle body stop screw (7) should not be touched again.

I purchased a connector and fabbed a pigtail.  In fact, I'm checking my TPS tomorrow morning.

[DucHead]

Here's the full write up (minus the pics):
"4V Desmoquattro Non Linear TPS Baseline Adjustment (plus ST3) - Written 06/08
Summary: How to set up 4V throttle bodies with the Non Linear TPS.
Discussion of idle mixture setting for various ECUS: P7 and P8, 1.6M and 5.9M.
Also for '04 and '05 model ST3.
Extra photos that I didn't have provided by Jan Krohn, Rich “Jasper” Bower, “Duc Wilder” Troy and Mike Currie from the 851/888 Yahoo list.
TPS fitment across all 4V models
Non Linear: 748, 851, 888, 916, S4, ST4, 996, S4R (Desmoquattro), ST4S.
Linear: 749, 848, 999, S4R (Testastretta), 1098.  Unlike the 2V models which have a bolt on Linear TPS, most of the 4V models have it fixed (peened over, etc) into the throttle bodies themselves, and are not replaceable as such.
Two different sets of throttle bodies have been used on the Desmoquattro 4V engine bikes since the release of the 851 in '88.  Both have been available in either single or dual injector configuration.
The second style throttle bodies have been used on all models from 888 onward, finishing in '06 with the last of the Desmoquattro engine S4R Monsters.  These also come in single or dual injector styles, and feature injectors that fit into the throttle bodies, with only the connector protruding.  888, S4, S4R, ST3, ST4 and ST4S models have a fast idle mechanism.  888, S4 and S4R models have a fuel pressure regulator mounted on the cross bar.  All other models have the regulator in the fuel pump plate mounted in the bottom of the fuel tank.
The balance or synchronisation adjustment mechanism varies from two different types of rear throttle wheel screw adjustments on 888 and the large white nut on 916 and later models.
In the following photos you'll notice I've numbered all the parts in the same series as the 851 throttle body photos above.  That way, if I give a number, you know which part I mean.

Items viewed from the LH side.
1.   TPS â€" throttle position sensor
2.   TPS adjustment screws
3.   Injector “green side flow” IW724
A/ Mounting holes where the 748, 916 and 996 models have the screw lock wiring loom connector.

Items viewed from the RH side.
4.   Throttle cable wheel
5.   Throttle cable mount
6.   Throttle linkage rod
7.   Horizontal cylinder idle stop screw
8.   Where the vertical cylinder idle stop screw would be, not used
9.   Horizontal cylinder air bleed
10.   Vertical cylinder air bleed
11.   Throttle linkage adjustment nut
12.   Fast idle arm
13.   Fast idle adjustment lever locking screw
14.   Fast idle cable mount and adjuster
15.   Fuel pressure regulator mounting hole for models fitted with such.
To set the “Non Linear” TPS
Preparation: it's easier if you can get to the top of the throttle bodies to wind out the stop screws and disconnect the linkage rod ends, so I usually do this with the air box removed.  If it's a restyled ST4S or ST3 (or even an older ST series bike) that I don't have to pull apart for anything else then I do them without getting it stripped.  Anyone who's had to pull one of those bikes apart will understand what I mean.  Designed by someone with no respect for those who have to work on them.
TPS base line setting procedure (as we do it)
Every step is as important as any other, and the predominant aim of this procedure (apart from being “correct”) is repeatability and consistency.  We normally do it with the engine and throttle bodies cold.  This is simply the convention, we do it hot if we have to.
1. Disconnect the throttle cable at the throttle cable wheel (9).  Easiest to just take the cable out of the wheel rather than play with the adjuster.
If it's fitted with the fast idle system, loosen the fast idle adjustment lever locking screw (13) to let the lever move freely and not block the throttle from closing fully.  You can leave the rest of the fast idle system as it is.
2. Disconnect the throttle linkage rod (6).  On the 851 style throttle bodies you need to remove a little circlip.  On the later style you can pop off the plastic connector on the horizontal throttle body.  I use a pair of side cutter pliers with the taper side against the throttle cable wheel side â€" it pushes the plastic connector off nicely.  Otherwise (if you're not as confident as our repeated experience lets us be) you can wind out the throttle linkage adjustment nut (11) to make sure the vertical throttle butterfly is open more than the horizontal throttle butterfly.
3. Connect to the TPS by whichever method you are using to measure the TPS output voltage â€" back probing wires, Mathesis, DDS, etc.  You need to go into the outer two wires if back probing.  For models with P7, P8 or 1.6M ECU you can hook into the ECU connector as below.
4. With the throttle closed before you start you should be seeing voltage in the range of 300 â€" 450 mV, depending on the model.  I usually record this voltage, just in case I need to go back to it.  Remember, you need to have the ignition on when doing this, and you don't want to short out any wires.  Disconnecting the headlight or removing the headlight fuse can also be a good idea if you don't have a "lights on/off” switch.
5. Back off the horizontal cylinder idle stop screw (7) to allow the throttle butterfly to close fully and jam if snapped or pushed.  These screws are either 7mm or 8mm hex.
6. Open and close the horizontal throttle butterfly gently until the voltage stabilises at a minimum.  Do not snap the throttle butterfly shut, as this will jam the butterfly and may give a false lower voltage reading.  Usually the voltage at this point will be in the range of 90 to 170mV, most likely around 100.  Again, I usually record this voltage out of suspicion.
7. Once you've ensured the horizontal throttle butterfly is closing properly, reset the TPS to give an output voltage of 150 mV by loosening the two screws (2) and rotating the TPS as required.  These screws are usually 7mm hex head.  Tighten the two screws (2) and ensure the setting remains consistent.
8. Wind in the horizontal throttle body stop screw (7) until the TPS output voltage is at the required idle setting for your model (Desmoquattro S4R: 423 mV; 2.6°).  At this point for some models we would use the throttle angle the ECU is reading to set the “base idle” setting, as what the ECU is reading is more relevant than the actual voltage, as there is always variation.  However, you need some sort of diagnostic tool or software to read the throttle angle, so for many the voltage is as close as you can get.  It's still quite valid.  There's a table below of the specified settings, both degrees and nominal TPS output voltage for that degree setting.
Ducati didn't start specifying degrees of throttle opening for idle settings until the Mathesis diagnostic tool was released in 1998 as before that there wasn't a factory tool for reading it.  So any model prior to '97 had a voltage setting only, which was 300mV for anything that had air bleeds.  On models without air bleeds (all 851 models and 888SP4) it was simply whatever it needed to be to get the engine to idle.  You can see the 748 and 916 specified settings changed a little from the 300mV once a degree setting was given.  If you have a USA or Swiss spec bike the decision on which settings you use is up to you.
The relationship between degrees and voltage under 30 degrees throttle opening is: mV = (degrees x 105) + 150
Model   TPS Voltage - mV   Degrees
748   287   1.3
748 USA   344   1.85
748 Swiss   308   1.5
748R   381   2.2
851   Whatever makes it idle   n/s
888   300   n/s
916   318   1.6
S4   339   1.8
ST4 Euro   344   1.85
ST4 USA   402   2.4
ST4 Swiss   402   2.4
ST4S, S4R   423   2.6
ST3   423   2.6
996   423   2.6
9. Open and close the throttle a few times to check the idle setting is stable and adjust if required.  The TPS is now set and the horizontal throttle body stop screw (7) should not be touched again.
If you removed the throttle linkage rod (6), refit it now.  If you adjusted the throttle linkage rod (6), set it back to its approximate original position.
Reconnect the throttle cable to the cable wheel (4) and set the free play in the cable.  You can do this at the throttle body (10) or the twist grip, up to you.  Turn the bars fully left and right while doing this just in case the cables move when doing that.  Remember on a 748, 916 or 996 the RPM given by the fast idle button will determine the cable free play pretty much.
For those bikes with the fast idle lever set the fast idle as desired by tightening the fast idle adjustment lever screw (13).  I prefer to have a fair bit of clearance here so that full fast idle gives no more than 3,000 RPM, but some people like to just move the lever a little and get the fast idle acting.  Personal preference pretty much.  Just make sure the fast idle adjustment lever (hidden inside the throttle cable wheel (4)) has some clearance and therefore no effect at closed throttle.  This can be a bit fiddly as you have to try to hold the fast idle adjustment lever and the throttle cable wheel (4) while tightening the fast idle adjustment lever screw (13).
At this point I would usually refit the air box, etc and put the fuel tank back on.  You can get to all the adjusters you need to from the sides, some can be a bit fiddly though.
Wind the air bleeds (9, 10) fully in, I usually record how far out they were, just in case I need to go back to where I started.  You should need the fast idle on (if fitted) to get the engine to idle.  Set the manifold vacuum balance (synchronisation) via the balance adjustment nut (11) or throttle linkage rod (6) nuts using mercury sticks, etc at various RPM.  This is often a case of best compromise, and remember that cruise at 4,000 RPM has more throttle than free rev at 4,000 RPM.  I usually go up to 6,000 or so RPM free revving to check for variation.  It's not uncommon to see one cylinder lead then the other lead at differing RPM.  Remember the word “compromise”.
Next set the idle speed using the air bleeds (9, 10) as required.  On the 851 models just use the horizontal idle stop (7).  Set the idle speed at approx 1100 â€" 1150 RPM once the engine is hot.  There is no general rule for how far out the air bleeds should be.  At this point most will set the air bleeds so the cylinders are balanced at idle.  We don't worry about vacuum balance at idle though â€" we balance the mixture using the air bleeds and idle trimmer, as set out below.
That's the end of the throttle body fiddling.  Next is the setting of the idle mixture.  I often say to people that if they can't carry out this final step then all the previous steps may have just been in vain.  You might get lucky and be close.  Or not lucky and still have a poorly idling or running bike.  The idle mixture can have a very large impact on general running at low throttle openings.
For example, if the bike is too lean and idles low, winding out the air bleeds (9, 10) to try to raise the idle speed will only lean it out more, so the idle will most likely not increase.  You can sometimes make a bike idle better by winding the air bleeds (9, 10) in and richening the idle mixture if it was too lean to start with, even though the idle is low.  As an indication based on experience, a full turn on the air bleeds can change the mixture from 1% CO to 4% CO, so the air bleeds have a big affect.
To adjust the idle mixture you need to get into the idle trimmer
We use 4 to 5% CO as the idle mixture target for all Ducati models.  This tends to work well and give good low speed running and fuel economy.  We take a sample from both header pipes using the little 1/8 gas threaded bungs.  You can buy from Ducati a tube to go into this bung â€" it's a piece of copper pipe with the appropriate fitting on the end â€" that is surprisingly cheap.  You could also get some made up by a local hydraulics supplier.  We have a few of varying lengths and bends.
Given there is only one idle trimmer for both cylinders, we check the mixture and then adjust the trimmer to get the average between both cylinders where we want it.  Then we adjust the air bleeds to give the same mixture in both headers.  This means that the manifold vacuum balance or synchronisation at idle will often not be equal.  That's just how it is.  Equal mixture CO% is more important in my experience.
S4, S4R and ST4S models with 5.9M ECU
The 5.9M and 5AM look like this:

The idle trimmer on these models is adjusted electronically via the following diagnostic tools or software.  There is no way to get around it.  “Stand alone” means a separate, hand held unit.  “PC” means run via a PC or laptop."

I found it by Google search.

[TJR178]

Wow.  That's a lot to take in.

So you removed the fast idle lever/cable?  Interesting.

What kind of equipment do I need?  The closest dealer to me is about 2 hours away, so I'm more into doing the work myself.

Thanks for all the info pompetta!

[DucHead]

Holy hell!  I think it's easier for me to take it in.  I don't have any of that equipment. 

Thanks for that write-up though!

I'm just using a voltmeter, but I do have the software.  Come on down! 

[TJR178]

I'm just using a voltmeter, but I do have the software.  Come on down! 

I wish I could man!

[DucHead]

Here's a pic of the pigtail I made:


I purchased the pins and connector here: http://www.eagleday.com/ampconnectors.html  , but I'm sure they could be sourced lots of places.

[Lieutenant Dan]

DucHead,

How did you know where to connect those leads?

Dan