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Discussion Starter · #1 ·
Problem setting ST4s fuelling – any help will be appreciated.

Bike is 2001 ST4s, 22000 miles, recently serviced, generally running well, but it has never gone as well as my S4r monster did (both totally standard inc 15t front sprockets). Recently I’ve bought a 996 SBK and the ST is nowhere near as quick (The 996 does have a 14t sprocket fitted). I can squeeze 200 miles from a tank and still have a bit left, so it may be a bit too rich but its not extremely so.

I’ve been following instructions on Brad Black’s website, and have also read the Ducati factory manual and the Desmotimes book – all follow almost identical procedures.

This morning I’ve:
set the TPS to 150mv
screwed the air bleeds fully in
run the engine up to temperature and balanced the throttles using only the balance bar in the throttle linkage – vacuums are now balanced between idle and 5000rpm so I’ve left the air bleeds fully in
set the idle to 1200rpm
connect Technoresearch software and Gunson Gas Tester

Idle trimmer had been set to +15.

At this point I was planning to use the Technoresearch software to set 3-4% CO, but having stepped between zero and +40 on the idle trimmer, I cannot get the CO to rise above 1%.

I’m using the exhaust sensing screw in the rear downpipe (not the tailpipe exit).

Can anyone please suggest why I may not be able to get above 1% CO?
What sort of trimmer values are typical for a standard bike?

My gut feeling is that it’s running rich – my MTS1000 has an idle trimmer value of –3 (set by the local Ducati dealer) and is the crispest, sharpest bike I’ve ever ridden. I know that you cannot copy the value from another bike and expect it to be right, but I would expect Ducati to design the ECU so that your base line value should be zero and with a standard bike I wouldn’t expect to be far from that, and the MTS bears this out. However the gas analyser does not agree with my diagnosis.

I did suspect the gas analyser was faulty, but a quick test on a friends badly running carb 900, showed readings from 8-10% CO, so the analyser isn’t dead.

Any suggestions as to why I can’t increase the CO reading or what I should set the trimmer to would be appreciated.

Many thanks, Mark.
 

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Mark, are you using a starting point for the Gunson tester of 2.0 in open air as reflected in the instructions?
 

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Just to make sure I am clear, a few more questions. 1) Your post says your bike is a 2001 ST4s which, as I understand it, should have the older 1.6 computer on it and not that 5.9 computer introduced in 2002 which the VDST tool fuel mixture feature will communicate with? If your computer is the 1.6 version, the fuel mixture is set via the fuel trim/pot screw inside the computer box. 2) Starting from the base setting of 2.0 on the tester, when it is hooked-up to the exhaust port is your final reading 3.0? (2.0 + 1.0)? 3) You mentioned you are testing at the rear/vertical exhaust port. Have you also obtained a reading from the front/horizontal exhaust port? Also and with respect to a 5.9 computer, the VDST tool will allow you to set fuel mixture settings within a very broad range of -128 to +128. For reference, I have found that it is not unusual to see fuel settings in the low +40's to low +50's on 2002 & 2003 ST4s' running high flow air filters and aftermarket exhausts. Obviously, there are a # of things that could affect final settings (altitude, leaks/air bleeding into the intake track, etc.).
 

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Discussion Starter · #5 ·
Starting from 2.0 the Gas tester drops to the range 0.7 - 1.1 with the engine running.
I haven't tried the front cylinder yet - When I found that I couldn't control the rear cylinder reading on the gas tester by adjusting the idle on the Technoresearch software I stopped.
My bike is totally stock, so I was expecting to see a reading in the region of zero.

Thanks for the input.
Mark
 

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Just to make sure I am clear, a few more questions. 1) Your post says your bike is a 2001 ST4s which, as I understand it, should have the older 1.6 computer on it and not that 5.9 computer introduced in 2002 which the VDST tool fuel mixture feature will communicate with? If your computer is the 1.6 version, the fuel mixture is set via the fuel trim/pot screw inside the computer box.
I believe the ST4s was introduced in Europe as an MY 01 model, but it is the same bike that was introduced in North America as an MY 02 model. Therefore, the computers should be identical as well.
 

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Bill, just took a look at the ST FAQ site which confirms your understanding.

Mark,

I would check the reading on the front cylinder. Your post mentions that the bike is running rich but your reading is showing the contrary. It is exceptionally lean. A look at the spark plugs would also reveal if it is running lean or rich. Also, if you have the VDST tool, simply set the TPS using that tool.
 

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Discussion Starter · #8 ·
The richness is only a hunch - I'm not sure why now but I've always felt that it was a bit on the rich side. I haven't had the plugs out today, but last time I changed them they weren't excessively black. I will have a look at the front cylinder reading too.

As far as the TPS is concerned, my bike has the movable unit, you loosen a pair of screws and rotate the body to set the "throttle closed" voltage.

You are right that the UK 2001 bike is the same as the rest of world 02 bike. (I didn't correctly read your earlier post - I do have the 5.9ecu)

Something that I should mention - the bike has always gone well under load, but is uncomfortable on a neutral throttle, with a fair bit of snatching and rattling the clutch to and fro. The engine hunts and the load on the clutch basket & plates keeps on reversing.

I'm tempted to take it out tomorrow on a series of short rides and keep reducing the idle trimmer 5 points at a time to see what happens to the way it runs.
 

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As far as the TPS is concerned, my bike has the movable unit, you loosen a pair of screws and rotate the body to set the "throttle closed" voltage.

I'm tempted to take it out tomorrow on a series of short rides and keep reducing the idle trimmer 5 points at a time to see what happens to the way it runs.
Again, the VDSTS tool has the capability of resetting the TPS. My suggestion is you use the tool to do so. No need to physically mess with the TPS itself.

Assuming the throttle bodies are balanced with the bleed screws fully closed and have been verfied as being so via mercury sticks or other measuring device... now... reset the TPS using the VDSTS tool. Once the TPS has been reset via the VDSTS tool, use the Gunson tool to get readings off of both exhaust ports (i.e., both horizontal & vertical cylinders). If your CO readings for each cylinder are not between 3.0 - 4.0 on the Gunson tool, use the VDSTS tool to increase the fueling. Obtaining an optimal CO and idle balance can then be done using the respective bleed screws.

I believe your ride/adjust approach is not going to get the bike to a sound state of tune.
 

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Discussion Starter · #12 ·
I bought mine from Kitech Performance, who were listed on the Technoresearch website then. I see now that Probike is the UK distributor on their site. Its not the cheapest thing, I found that I paid in £ what the US dealers were asking for in $ but having been caught out by import duty when buying direct in the past I figured that it was the better bet. With the exchange rates now you'd probably get a better deal all round buying in £.

UPDATE -

I think I was bit out of step when I said I thought it was running rich. After getting a bit exasperated with it I arbitrarily richened the mixture by 5 points and took it out for a ride just to see what the difference was. The bike is pulling much more strongly with a better pickup from a rolled on throttle. Its not got the cleanest idle, so I've still got some work to do, but at least I've now got the 996 SBK grunt and response I wanted, and I can further tune the idle over the next few days.

Thanks to everyone for their input. Cheers, Mark.
 

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Mark, Good thread mate

BTW how did you find it right at the top of the rev band? I though that rich would be good low down and lumpy at 8-10K

Regards

John
 

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Discussion Starter · #14 ·
John,

Its pretty good throughout the rev band. I need to experiment further to get the idle set properly - at the moment its idling a bit fast, yet still stalling very occasionally, so clearly something isn't right, but once the throttle is opened its fine. Quite a bit stronger than before and a better response.

The key thing for me is the response - to be honest it was quick enough before but I do like an engine to feel crisp and sharp in the way it reacts to the throttle. The MTS has always had a better response and whilst it seems odd to criticise something thats faster, my ST has never felt as good on the throttle as the MTS does.

I think the key thing is that it probably isn't rich now, I suspect its right (or at least better) now and it was lean before. I was looking at the box that my Gas tester came in and theres a chart on the side showing how the engine response changes with air/fuel ratios. It says the engine will 'hunt' when lean and thats what I was getting, so maybe it was lean all along. I'm still a bit confused to be running +45 on the trimmer with a stock bike, but I guess the way it goes is more important than the number.

Mark.
 

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Again, the VDSTS tool has the capability of resetting the TPS. My suggestion is you use the tool to do so. No need to physically mess with the TPS itself.
No, the VDST tool cannot adjust the TPS on this model. It is necessary to do it physically. The tool can provide a reading of the throttle opening in degrees but it cannot make the adjustment.
 

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I'm still a bit confused to be running +45 on the trimmer with a stock bike, but I guess the way it goes is more important than the number.
The trimmer is there to compensate for normal production tolerances. If you have a very high trim number it could be your fuel pressure is a bit too low. If one cylinder is rich and one lean the problem could be with one of the injectors.

If you achieve a good CO reading on both cylinders and it's still snatchy at neutral throttle I would recommend checking the cam timing and also check the TPS setting again. It's easy to set a little bit off and it can make a real difference.
 

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No, the VDST tool cannot adjust the TPS on this model. It is necessary to do it physically. The tool can provide a reading of the throttle opening in degrees but it cannot make the adjustment.
Read the 7th bullet under the Technoresearch link below.

http://www.technoresearch.com/Products/VDSTS-Motorbike/VDSTS_Motorbike_Features.htm

Are you saying you have the tool and have actually attempted to execute a reset? If so, are you also saying the reset fuction, where the the tool essentially asks... are you sure you want to do this?... and... if the answer is yes, there is a count down and then the tool displays a pass or fail message, isn't actually resetting the TPS? It being understood we are talking about throttle openings measured in terms of degrees using this process and not an electrical current @ the TPS.
 

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Discussion Starter · #18 ·
Are you saying you have the tool and have actually attempted to execute a reset?
YES

If so, are you also saying the reset fuction, where the the tool essentially asks... are you sure you want to do this?... and... if the answer is yes, there is a count down and then the tool displays a pass or fail message, isn't actually resetting the TPS?
YES

The ST4s uses screws to allow you to reset the TPS by physically moving it. On the MTS you can work through what you've just described with the engine running and hear a change in the idle at th epoint where you reset the TPS. On the ST4s you don't get that.

The ST3 is probably a software reset going on its years of manufacture - but I'd need to check - so you would do that from the software.
 

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YES

YES

The ST4s uses screws to allow you to reset the TPS by physically moving it. On the MTS you can work through what you've just described with the engine running and hear a change in the idle at th epoint where you reset the TPS. On the ST4s you don't get that.

The ST3 is probably a software reset going on its years of manufacture - but I'd need to check - so you would do that from the software.
hmmmm? Mark, have you inquired with a representative of the tool what it is the tool is actually doing, with respect to an ST4s, when the TPS reset function is selected? Sure seems as though there is some form of check and verification being performed.
 

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Are you saying you have the tool and have actually attempted to execute a reset? If so, are you also saying the reset fuction, where the the tool essentially asks... are you sure you want to do this?... and... if the answer is yes, there is a count down and then the tool displays a pass or fail message, isn't actually resetting the TPS? It being understood we are talking about throttle openings measured in terms of degrees using this process and not an electrical current @ the TPS.
Yes, I tried the TPS reset function on my ST4s and it does not reset the TPS. I spoke with Giamberto at TechnoResearch who helped develop the product and he said the TPS would only be reset on ECU's that had that capability and the 59M of the ST4s is not one of them.
 
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