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2004 749S, 2006 MTS620
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Discussion Starter #1
Guys,

I am in the process of setting up the proper fuel trim for my 2004 749S with 6600 miles and am using a Gunson gas tester, Lonelec ECU cables, and the IAWDiag software. I have already done the following:
  • Very carefully adjusted the valves to .005” on the openers and .002” on the closing shims
  • New belts both correctly tensioned
  • Fresh ethanol-free 91 octane fuel running through a brand new OEM fuel filter
  • TPS correctly reset to both physically and electronically read 1.30 degrees (for the 749 bike….the 999 is different it seems)
  • Both throttle bodies were set up on a mercury stick to balance them at both idle and fast idle of 3000 RPM. They looked pretty good when completed and the engine did feel a bit smoother.
  • No improper tension on either the throttle cables or fast-idle cable
The bike was run up to temperature downwind from the shop so no CO would contaminate the gas tester…and the tester was calibrated for 15 minutes to reach full stability, then adjusted to read 2.0% and verified to remain stable at that number for five more minutes.

When the bike was initially started for the warm up and short ride to get it to temperature, the idle was the historically-normal 1000-1100 RPM. This has always seemed a bit too low as I am really wanting 1250 RPM as that “feels” right when on idle and is what the manual calls for. More on this in a minute.

Once up to temperature and then quickly brought into the shop for hooking up, I did the following:
  • Verified on the laptop the idle was hovering in the 1050 RPM range (normal ever since I bought it brand new)…this also matched the bike’s tach, too
  • Fuel trim was at “0” on IAWDiag
  • Hooked up the gas tester to the rear/vertical cylinder
  • Tester reading stabilized at 1.7% CO…which is sort of what I expected as the factory sets them around 1.5% for emissions purposes
  • Started incrementing up in five-point jumps to richen the mixture; as I got to 30-40 points the bike really smoothed out and the idle noticeably picked up…CO was in the 3.0% range
  • Shut bike down…cleaned out the shop air with fans….and re-calibrated the gas tester over the next 20 minutes to get a fresh start and clean sensor
  • Started again at 40 points and went up to +65 when the engine seemed to very slightly stumble a bit although CO read 4.5%…backed back off to 60 points and stumbling went away…backed off to 57 points and CO stabilized at 4.1%
  • Shut the bike off with final reading on the rear cylinder: fuel trim at 57 and CO at 4.1%
Now, what really caught my attention was the idle…with no tension on any cable…was hitting a constant 3700 RPM when the CO was reading 4.1%. So, by only changing the fuel trim and nothing else the idle went from 1050 RPM to 3700 RPM. I knew I was adding fuel to the engine but did not realize it would change the idle so drastically. So, I have stopped for the day and am scratching my head on what to start with tomorrow?

Should I look into dropping the fuel trim from 57 down to some lower number and see what happens? The CO will clearly go down but so will the idle.

Thanks!

Head Tomcat
 

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sounds like the air bleeds are way too far out. trimmer at +60 is nuts.

this is pretty simple stuff. wind the air bleeds fully in and set the running balance / sync for best compromise. wind the air bleeds out to set the idle speed. adjust idle trimmer to get the mixture you want. readjust air bleeds to reset the idle speed if the speed changes a lot.

i would expect the trimmer to be in the -5 to +10 range.

otherwise i would think it's got a big vacuum leak somewhere.
 

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To add to belters post. If you want the idle higher, wind in the throttle stop screw AFTER you set it up to spec.
 

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do fucking what! lordy, lordy lord.

(curls up into a foetal ball on the floor and rocks gently)
You do the higher idle adjustment with the trim and air? Never done that. I have always set the bike to stock values and adjust for a higher idle with the stop screw. Have I been doing it wrong all these years Brad?
 

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yes.

you don't ever adjust the idle stop on a linear tps engine. if someone else comes along and does a tps reset, the relationship is now wrong as the throttle angle is greater than the ecu is reading.

or after you've set the idle stop setting on a non linear tps engine. idle speed adjustment on non idle control valve engines is always air bleed based.

but, really though, you know, do whatever you want. whatever works for you.
 

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I do understand this. Have had a few bikes fitted with powercommanders that don’t start at good base settings. Anyway, that’s the way I’ve always done it. Tuning carbs for so long does this.
 

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2004 749S, 2006 MTS620
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Discussion Starter #8
Guys,

I am starting this process over again today and have been carefully looking at all the settings. I still cannot for the life of me figure out how setting the fuel trim (even very high at 57) could so dramatically increase the idle...from the historical 1100 RPM to now 3700 RPM. TPS setting is still right at 1.30 degrees as it has always been (yes, the butterflys are also physically set to that, too) and the throttle cables have been re-verified as having proper slack.

And now back to the two TB bleed screws and what I am finding...

The bike is a 2004 749S model and sat in storage for about three years as the old Ducati dealer had long ago lost interest in Ducs and did not hardly market/service at all. Sometime in this period I understand it was taken from the crate and lackadaisically run up...and exhibited the well-known 2004 749S stalling tendency. The old dealer apparently tried to remove the stall and could not do it. A new dealer bought out the sinking franchise in late 2006 and the 749S came across in the deal with the rest of the Ducati business. I bought the bike in Feb 2007 and have had it since.

When I got the bike, I had the new dealer install a slip-on Termi system....first question....did this slip-on come with a "Race" ECU or did that only come with the full Termi system? How can I tell...does the instrument panel in any way indicate this when the ignition is on or do I have to physically look at the ECU and decipher it?

Second question (and likely the big one)...it has been very clear to me that some ham-handed mechanic (at the old dealer!!!) had long ago already been working on the two TB air bleed screws as their slotted brass heads were slightly burred up with a poorly fitted screwdriver and a bit too much force. More importantly, in order for me to get the two TB's to balance the front/H screw is all the way in while the rear/V screw is 1 1/2 turns out. On the surface this seems utterly wrong as I would expect them to be out roughly the same amount...and most certainly the front/H bleed would NOT be all the way in!!!!!

I have worked on carbs for several years and have seen where Magilla the Gorilla has over-turned brass adjustment screws and damaged their needles and seats to the point they had to be replaced. Could this have happened many years ago to the front/H bleed screw and I have suffered with this ever since and been unaware of it? I careful looked at the factory parts manual and there is no detailed breakdown of the TB assembly...and especially the two TB bleed screws. If I want to inspect the two bleed screws, can I just remove them and be careful they do not drop into the nether regions...or is there a spring, ball bearing, gasket, funk, etc. which will pop out and surprise me?

I am very suspicious of the front/H screw being all the way in and the rear/V seems "about right" to me.

Whew...and thanks so much!

Head Tomcat
 

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Discussion Starter #9
More information...and this time it is much better!

I started over again from ground zero and re-verified the TPS was physically/electronically the same at 1.30 degrees. Throttle and fast-idle cables were slack and all seemed well. I took out the front/H TB air bleed screw to see how it operated and nothing (thankfully!) was special. Just a finely finished brass screw with a thick taper on the working end and a rubber o-ring to provide tension and air sealing. It looked clean with no issues...though I made sure to carefully swab out the air channel in case some minor debris was hanging around. I could not fully remove the rear/V bleed screw as the fast-idle bracket was in the way...so I carefully screwed it out as far as possible...carefully checked its o-ring for integrity….and saw all appeared well. It went back in, too.

Then I started the mercury manometer setting again with fast idle being established first. The engine was warmed up and the IAWDiag fuel trim was reset to 0. This went well and the 7mm hex-head screw was essentially in the same position as yesterday once balance was achieved at 3000 RPM. I did notice the idle was now returning back to its normal 1100 RPM which was interesting to me as I ended yesterday with it 3700 RPM. I am wanting to hit 1400 RPM or thereabouts.

Suddenly, the idle picked up rapidly from 1100 RPM and started running toward 4000....with nothing apparently touching the bike at all.

I jumped up from the left side of the bike where the laptop was connected to the ECU and immediately saw....the front/horizontal manometer tube had heated up enough from the fast-idle session that it had loosened up and slipped off the vacuum barb! As this was on the RIGHT side of the bike I would not ever have seen it if I had remained sitting on the floor with the laptop...on the LEFT side of the bike. Which is exactly was must have happened yesterday.

Quickly placing the vacuum line onto the barb, I secured it with a wooden clothespin so it could not slip off again...and made sure the vacuum was not restricted, either. The idle went down immediately to 1200 RPM.

From there I iterated on slow idle with the two air bleed screws and got a lot more satisfaction this time. Carefully adjusting both screws gave me a reliable idle at 1300 RPM with the manometer being fairly balanced. It ended up with the front/H screw being 3/4 turn out and the rear/V being 1 turn out.

Setting up the Gunson gas tester over the next hour with focus on the rear/V cylinder...and setting the fuel trim started. After several minutes I got the V cylinder to read 2.60% CO at a fuel trim setting of 11. Going up to 13 and then down to 9 clearly had the engine change tone...and 11 seemed to the optimum point. I really wanted to get a higher CO reading but when balancing idle, engine smoothness, throttle pickup/deceleration...it just seemed that 11 points and 2.6% CO was best for this specific 2004 749S. As importantly, the idle was running a reliable 1425 RPM which matched on both the tachometer and IAWDiag screen.

Final specs for today:
  • TPS stable at 1.30 degrees
  • Both cylinders balanced at low/fast-idle speeds
  • Fuel trim set at 11 points
  • Idle is reliable at 1425 RPM
  • Rear cylinder had CO reading of 2.60%
Right now I am taking a break and will start tomorrow on setting fuel trim for the front/H cylinder to hopefully hit 2.60% with minimal adjustment on the air bleed screw...as I understand IAWDiag trim affects BOTH cylinders at the same time. Thus, the front/H cylinder will have its CO set manually via the air bleed screw.

What a day!

Head Tomcat
 

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Discussion Starter #11
I am willing to give it a try...what is your way to do this? Turn in the two air bleed screws to almost closed - which should lower the idle and also bump up the fuel richness - and then go back to IAWDiag and further richen the fuel trim to bring up the CO percentage? If so, this seems to indicate going up from the current setting of 11 points...to possibly 15-17 or so for this specific 749S to hit the 5% CO level.

One further note is that I saw the engine was clearly running cooler after all the work today as the fan came on a lot less. The fan starts at 215F and several times today I had to check if it was working...temp was floating around 203-205F most of the time. Big difference from when I first started this tuning a short time ago!

Head Tomcat
 

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i set the air bleeds to give the idle speed i want. then i check the mixture on both cylinders and adjust the idle trimmer to give sort of what i want, then use the air bleeds to fine tune it as required.
 

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Discussion Starter #13
Done!

I ended up with a CO of 4.5% on both cylinders with a IAWDiag setting of 20 points. The two air bleed screws ended up all the way in and lightly seated, then backed out 1/8 turn each. I probably did not have to do this but have a problem with brass vibrating against the harder aluminum allow TB base. So....1/8 turn out got them away from direct contact and did not affect the idle that I could hear or see on the tach.

Idle ended up a bit higher than I wanted at 1400 RPM but that is the lowest I could go at this time.

Both TB's are balanced at low/high speeds and react in unison with each other, too.

On a 95-mile test ride yesterday I immediately noticed the bike was running noticeably smoother, gear changes were smoother, acceleration was excellent and deceleration was truly wonderful! No popping or roughness as the RPM's wound down and a very nice "burble" sound, too. One thing I also noticed was the bike was running about 10-12 degrees cooler on the average.

Time to have some more fun with the 749 and later this summer will start on the 2006 Multistrada!

Head Tomcat
 

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Discussion Starter #15
I agree.....the idle is a bit high for my liking right now.

Since the two air bleed screws are each lightly seated/backed out 1/8 turn there is effectively no more adjustment left, would I now turn the 7mm screw which balances the two TB plates? I know that by turning the screw CCW it raises the RPM as the plates begin to move and let in more air. So if I rotate the screw CW it will lower the RPM...but will it affect the current fast-idle balance? Or, is the difference so minor that a difference could not really be felt?

Thanks!

Head Tomcat nearing the end
 

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the 7mm screw is for balancing the throttle opening via the manifold vacuum, done with both air bleeds wound full in. that's it's only job. nothing to do with idle or speed, etc.

the base idle stop is on the vertical throttle body. if you're going to adjust that you need to make sure it's done so that the referencing is correct.

taken from here - BikeBoy.org - DucatiLinear Throttle Position Sensor setting notes for all models 08/08 it talks about the mathesis because it's old and we were a dealer and that's the tool used and it was written in micromanaged style for other techs in the workshop to follow so that the result was what i wanted. but you just use your diagnostic tool to reset and read the tps output.

749 / 999 TPS setting procedure

  1. Disassemble bike to allow access to air box lid and inside air box – i.e., tank, side and front fairing panels and LH air conveyer and air filter.
  2. Put plenty of free play into throttle cable
  3. Make sure the fast idle lever on the rear throttle body LH side is seated against its stop. Add free play to cable if not seated.
  4. Wind the balance screw on the throttle linkage rod at the front throttle body 1 turn clockwise to open front butterfly more than the rear.
  5. Drill an 8mm hole in top of air box using the first “1” of the moulded-in part number 24610731A as the reference point. The hole is to be 45mm to the left of the “1” and 5mm back from the base of the numbers.
  6. Through the hole the throttle base idle screw will be visible. Remove all yellow paint so the screw can be wound out. Wind the screw out (2.5mm hex) until the TPS voltage reading stops reducing, plus an additional half turn.
  7. Make sure the rear throttle butterfly is not being held open by the fast idle lever and that the butterfly is snapping shut. Add more throttle cable free play if required. Wind out the base idle screw more if required to ensure TPS voltage has stopped reducing.
  8. Connect Mathesis to diagnostic connector and enter “Diagnostics”.
  9. Go into “Active diagnosis” and then “TPS Reset” and carry out a TPS reset with the throttle fully shut.
  10. Then go back into “Parameter Reading” and check the TPS degree setting. It should be approx 1.3 for 749 or 2.3 for 749R and 999. Whatever it is, wind the idle stop screw in until double this degree value is reached – i.e., 2.6 or 4.6.
  11. Go back into “Active Diagnosis” and carry out another TPS reset.
  12. If you then go back into “Parameter Reading” and check the TPS degree setting, it should be approx 1.3 for 749 or 2.3 for 749R and 999.
  13. Wind the balance screw on the throttle linkage rod at the front throttle body 1 turn counter clockwise to return the front butterfly to its original position.
  14. Reset the throttle and fast idle cable free play as required.
  15. Plug the 8mm hole drilled in the air box cover using an 8mm (5/16) grommet and tape over. Mark air box above vertical air bleed access hole with red paint to indicate procedure carried out.
  16. Refit fuel tank so bike can be started.
  17. Run bike and reset running balance with air bleeds wound all in. Then set idle speed and mixture using air bleeds and idle trimmer as required.
once you set the idle stop screw, you don' touch it again. to change the idle speed, you use the air bleeds. the idle speed should be too low with the air bleeds full in.
 

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Discussion Starter #18
I have done the airbox mods described above and then adjusted the 2.5mm grub screw to achieve both a physical and electronic setting of 1.3 degrees. Based on the existing yellow paint used to "protect" the grub screw, it appears no one else had yet been into the bike and worked on the TPS component. The air bleed screws had been previously worked on for TB balance...but it did not appear the TPS component had been touched. So, I removed the paint and then very carefully went through the process (several times) to physically/electronically reset the TPS to 1.3 degrees. I got a repeatable number and then called it completed.

One point to note is when I first hooked up IAWDiag to the ECU, the initial reading I had for the TPS position was 1.2 degrees. So, assuming the butterflys had not been earlier messed with as shown by the yellow paint still on the screw, this tells me that 1.3 degrees was likely the initial factory setting because if it had been 2.3 degrees I should have had a different reading not so close to 1.3...ie, IAWDiag would have read something like 2.2, 2.4, etc. and not substantially lower at the original 1.2 degrees.

This brings up a question in my mind involving this 2.5mm screw...

To achieve an idle of around 1200 RPM or so, it seems that given the production tolerances of building a bike, one method to consider when setting the idle is to slightly iterate on the 2.5mm grub screw to achieve that 1200 RPM idle and then reset the TPS to read 1.3 degrees. In other words, the physical location of the butterflys might not exactly be 1.3 degrees but are very close. The ECU is electronically reading them as 1.3 degrees and thus all downstream mapping, etc. remains as per normal.

This would seem to account for all production tolerances when the bike was built and achieve the desired idle RPM...while at the same time allowing the ECU to perform as normal.

Based on my recent experience, I figure no more than a quarter turn out of the 2.5mm grub screw would slightly change the physical location of the butterflys and lower the RPM down toward the desired 1200 RPM range. From that, a IAWDiag reset of the TPS to 1.3 degrees would electronically bring things back to spec.

Head Tomcat
 

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Discussion Starter #20
Well.....I guess not!

So far I have managed to get all the parameters correct with the exception of idle. According to the manual it should be 1200 RPM +/- 100. So, the accepted range is 1100-1300 RPM. Right now with everything adjusted I am at 1400 RPM and that is with the two air bleed screws lightly seated and then backed out 1/8 turn simply because I do not want brass vibrating against alloy. When they were both lightly seated the idle did not change...so, 1/8 out appears to be so small an adjustment that it has no measurable affect.

I followed BikeBoy's airbox procedure and did exactly what was stated. From what I am reading, the purpose of working with the 2.5mm grub screw is to physically place the butterfly's at a specific angle which matches what the ECU is programmed to read...in this case of the 749....1.3 degrees. To my way of thinking, if the butterfly's are physically at 1.3 degrees and the TPS is reset to electronically also read 1.3 degrees....then all further movement of the butterflys and TPS sensor will be aligned to each other.

Now, my issue is the idle is about 100 RPM too fast per specs and I am looking how to reduce this. Given my butterflys are now aligned to the TPS sensor....and the two air bleed screws are pretty much out of allowable adjustment...the TB's are balanced at both low/high speed....what else can be done to lower the idle?

The current CO reading is 4.5% on both cylinders and as the fuel is enriched the idle tends to go down as the mixture is less lean. Would slightly increasing the current CO fuel trim of 20 points to say 22 or so allow more fuel in...slow the idle a bit...and give a slightly higher/better CO reading of about 5%?

I guess my question is...given I have done about everything I can think of to get the bike running correctly...what is left for me to do to achieve a slightly lower idle?

Thanks so much!

Head Tomcat
 
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