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Maintenance and Issues




Information on setup and use of JP Diag and IAW Diag ECU diagnostic Software

ECU Installed in 2002 ST4s: Magneti Marelli IAW 59M  The TPS is PF09

IAWDIAG ECU Diagnostics Software and ECU Reader and Writer

Info and How to for Superseal 1.5mm AMP connector pin removal and assembly


2002 Ducati ST4s Manuals:

Work Shop Manual (large file +35Mb but text searchable) 

Electrical Schematic

Parts Manual

Owners Manual (IT, EN, FR, DE)

Ducati ST FAQ (Perry Rosenboom - Archive Copy v1.4)

Handy Capacity Values for ST4s:
Oil Quantity 3.7L ~ 3.9qts
Coolant Quantity 3.5L ~ 3.7qts
Fuel Quantity 21L ~ 5.5gal

Front and Rear Wheel Torque Values

  Ft-Lbs N-ms
Front Axel nut -- 28mm socket for nut 46 62
Front Axel Pinch bolts -- 12 mm head 14 19
Front Brake Caliper retaining screw 30 43
Rear Axel nut -- 30mm head 61 83
Rear Chain Adjust bolts -- 12mm head 5.9 8
Front Sprocket Plate bolts -- 8mm head 4.4 6

Oil Change Related Torque Values:

  Ft-Lbs N-ms
Oil Filter Cartridge 8 11
Oil Drain Plug 30 42
Oil Mesh Screen 30 42
Oil Mesh Screen outer Cap 30 42

Engine Mount Bolts Torque Values

  Ft-Lbs N-ms
Rear engine mount bolt -- 12mm bolt thread

(14mm bolt head, 15mm nut)

45 60


Link to Other Torque Values


1.  Battery would not maintain a charge

2.  Brake reservoir cap corroded

3.  Lower steering head bearings corroded and seized

4.  Installation of Evoluzione license plate re-locator

5.  LCD display module partial failure and repair

6.  Relay failure

7.  High coolant/water temperature under normal running conditions

8.  Output shaft wear and front sprocket retention plate wear

9.  Radiator Pressure Cap part number incorrect in the Ducati Parts Catalogue.  Correct PN is:89310031A

10. Brake Shudder / Judder / Chatter

11. Neutral Switch Failed

12. Tensioner and Idler Pulley Bearing (timing Belt) Replacement: Tensioner and idler bearings are not the same!!!

Idler Bearing PN is: SKF 6003-2RS1/C3GJN (GJN is grease spec, high temp)

Tensioner Bearing PN is: SKF 61904-2RS1




Events and Receipts

1.  600 mi First service

2.  3,000 mi oil change

3.  6,000 mi service

4.  9,000 mi oil change

5.  12,000 mi service

6.  15,000 mi service

7.  16,400 mi service

8.  18,500 mi service

9,   24,000 mi service

10. 30,000 mi service


Install and Set Timing Belt Tension Values using acoustic vibration:

Measure and set Tension on timing belts:  110Hz on new Ducati OEM belts and approx 90-100Hz on existing belts. Set tension at 100Hz for New Exact Fit belts (CA Cycleworks).

To set the belt tension, the cylinder you are checking MUST be at TDC so that there is no tension applied to the belts by the closing springs pushing on the rockers.

1.  For the horizontal cylinder it is the forward run between the tensioner pulley and the exhaust camwheel (posn 21).

2.  For the vertical cylinder it is the rearmost run between the idler pulley and the exhaust camwheel (posn 25).


Suspension Info

Fork Overhaul and Oil Replacement - Ducati ST4s Showa Forks ('02-'03 Ducati ST4s)

Fork Overhaul and Oil Replacement - Ducati ST4s Showa Forks ('02-'03 Ducati ST4s) - pdf

Preload (24 Dec 20)

F1   R1  
F2   R2  
F3   R3  
    Front Rear
1-2 Static Sag    
1-3 Rider Sag    

Ohlins recommendations:

    Front Rear
1-2 Static Sag 15-30 10-20
1-3 With Rider 35-50 25-40

*measurements in mm.

25 December 2020

Front Rear
Compression Damping    
Rebound Damping    

Tire Pressures: Front- 33PSI; Rear- 35PSI


IAW DIAG Setting Trimmer Value

IAW5xM ECU has two types of memory:

Flash-Memory, where the bin-file (aka fuel map) is stored and EEPROM - electrically erasable programmable read-only memory, where data like Serial number of ECU, TPS-Valence-Trim-Value and is stored

When you flash your ECU, it does not change the EEPROM (you may see the eeprom-tool from the guzzidiag-page) therefore, it is not necessary to complete a TPS Reset if you reflash an existing ECU in your bike (No change to the TPS-Valence-Trim-Value stored in EEPROM)

It is not harmful, but it is not necessary. Only changing the Hardware (ECU or TPS) makes it necessary to do a TPS Reset, or a worn TPS.

For the CO-Trimmer Setting:
The 5AM ECU operates stock in Closed Loop Mode, and the CO is controlled by Lambda sensors. The Value of the CO-Trimmer is set to zero from factory,
you canít even change this value as long Lambda sensors are active.

If you reflash the ECU with a map "Lambda off" -- as described above the Trimmer-Value remains at Zero.

The bike will run, even with no change to the CO-Trimmer.   It will run much better in the Low/mid-rpm range, if CO is set to around 4.0 - 4.5% as measured with a gas-tester.  If no gas-tester, set the CO Trimmer to a value of around 24.

According to those with experience, CO level of 4.0 -  4.5% equates to a trimmer value between 22 and 28.

ST4s Non Linear TPS - Set Baseline Adjustment

Brad The Bike Boy has a comprehensive page dedicated to this with the CAUTION: Do NOT connect Diagnostic SW and press "TPS RESET" - NO!  Do NOT do it if you have Non Linear TPS (like my 2002 ST4s does)


pdf printed version of Brad The Bike Boy's TPS instructions


Vinnie's info on TPS Reset

Follow Brad the Bike Boy's instructions.

I back probe the TPS at the connector, red lead (+) from my multi-meter to the #2 wire (orange) in the middle of the connector, and my black lead (-) to the #3 wire (black & violet).













Other ST4s Issues/Troubleshooting Info

1.  ST4s wouldn't rev above 4k






1st Issue...  Battery would not maintain a charge:

        Replaced the Battery and Cables and added Headlight Gizmo (see the Mods page)



2nd Issue... paint peeling and corrosion of the brake reservoir cap

        Noticed paint peeling and corrosion of the (aluminum?) cap.  I don't park it on the side stand and there is no trace of brake fluid leaking.  L  21 Months after purchase...  wonder if it is covered by warranty?  Well So far, no word on warranty.   Ducati Nashville did order and replace the cap.  $25 for a new one.  The original problem was the rubber seal in the cap had developed a leak (pin hole) and the fluid caused the cap paint to peel and corrode.  There was a small amount of brake fluid between the seal and the cap that caused the problem.



3rd Issue...  Lower Steering Head bearings corroded and seized:

        This issue was first called to my attention by Ian of www.st4s.com.  He pointed out that several ST4s owners had a similar problem and encourage current ST4s owners to have it checked, especially while under warranty.  Very sound advice.  I had mine looked at during the 6,000 mi service and look how bad the bearings were.  Click on the photo for a more detailed picture, or click here for a very high resolution photo.



4th Issue...  Not a maintenance issue per se, but the License Plate Relocator Kit from Evoluzione doesn't quite work as advertised.  The result is that the turn signals interfere with the saddle bags (Panniers).  I found a short stalk on LT Snyder's Desmo Times to modify the rear turn signals and the last photos shows them installed with the panniers attached.  Great fix!








5th Issue...  LCD Module display (LCD Panel) partial failure.  About a month after a very rainy and wet ride, my LCD display started to fail.  It would only display the top half and lower right portion of the display, I could see temperature and time, but only half my tank of gas.  This seems to be a common problem or so I have read on some of the forums.  I spent the time on a cold Sunday afternoon and removed the LCD module and set about repairing it.  This is how I did it: 

Click on any of the photos for higher resolution image

    1.  Remove the upper fairing to get at the instrument mounting plate.

    2.  Disconnect  the speedometer (odometer) cable.

    3.  Remove the bolts attaching the instrument mounting plate.

    4.  Detach the instrument cluster from the mounting plate.

    5.  Remove the single cap nut from the back of the LCD module and disconnect the two pig-tail electrical connectors.  (the connectors will pass through the back of the housing one at a time with care.

    6.  I placed  the LCD module on a towel and removed the three small Phillips head screws.


    7.  Using a sharp sturdy blade, drew along seam at the bottom of the module until cutting the glue bond,  then using a small flat tip screwdriver worked the plastic halves apart by slowly and gently first the bottom half then the rest of  the module.  (you can see I accidentally scored a bit of the plastic)


  8.  Once halves of cover are apart, remove the LCD display and circuit card assembly.  My LCD module had a considerable amount of water in it and corrosion on the circuit card.  Used a Q-tip with a little contact cleaner to remove the corrosion,  then used a dry Q-tip to remove any residue.



    9.  When I put it together, I used black silicon RTV all around the edges of the two halves and the three screw holes.  I also used RTV around the grommet where the electrical pigtail passes, I think that is  the culprit that allowed the water into the LCD module in the first place.

    10.  Update:  After 12 years, the trip computer LCD display started to fail again. Much more significant than the first time, loosing portions of temperature display, fuel bars, etc.  I attempted to clean corrosion again but this time to no avail. I did notice that water intrusion seems to be occurring through the time set button. I did have some significant weather during the May 2021 ride at ECM and it sat through a big storm while parked at Fontana Dam Resort and even though the bike has been dry since, and garage kept, the display failed and still has some water inside. I opened it up and saw a few little droplets sticking near the time adjust button.
I purchased a replacement via eBay. I did place preemptive RTV around the back grommet where the electrical pigtail passes of the new display. I am thinking through some additional protection around the time adjust button but do not want to have it prevent the use of the button. Tiny little clear silicon around the circumference of the button perhaps, but do not want the button to stick.



6th Issue...  Relay failure of primary relay located next to fuse panel under left side instrument trim.  Replaced with Duralast Relay PN# 19283


other relays that can be used are:  preferred: Siemens V23073 & V23074 and Tyco A1001-A402 & A1001-A403


Bitron B047E 46520411-232006 & 232008
Borg-Warner (BWD) R3223
BMW 61 36 1 393 412 & 61 36 1 393 415
Bosch 0-332-207-307
Ducati 541.4.003.1A & 541.4.010.1A
Ford F57B-14B192-AA
Hella 4RD 931 524-02
Hongfa HFV6 012ZS-TR & 012HS-TR
NAIS ACM13221 & ACM33221
Omron G8HN-1A2T & G8HN-1C2T
Siemens V23073 & V23074
Song Chuan 871-1C-S-R1-12VDC
Tyco A1001-A402 & A1001-A403
Zettler AZ988-1CT-12DC1R(201)



7th Issue... High coolant/water temperature under normal running conditions.  Drained and flushed cooling system (used Liqui-Moly cooling system flush) rinsed and refilled with Engine Ice.  Temperature sensors replaced, and replaced radiator pressure cap. ** Note the part number for the pressure cap is incorrectly shown in the Ducati Parts Catalog.  Got it straightened out with Ducati North America by working with Ducati, Omaha...they are super.  Checked the water pump impeller, all looking good; refitted water pump housing.  Straightened radiator cooling fins.  Second Cooling Fan Installed - Right Side, manual switch controls both fans.




8th Issue...  Output Shaft wear in the channel caused by front sprocket retention plate, due to misaligned chain!


The donor sprocket below and the resulting spacer after machined down:


spacer in place:



Installed and chain aligned!!!  Note the difference in swing arm reference marks with the chain CORRECTLY aligned!!!





9th Issue...  Radiator Pressure Cap part number incorrect in the Ducati Parts Catalogue.  Correct PN is:89310031A

Listed in the ST4s Parts Catalogue as, PN 893.4.006.1A  (CATALOGUE No: 915.1.130.1A , ISSUED: 05 - 01) which is NOT the right Part Number for the cap required.  Use Ducati Part Number 893.1.003.1A


10th Issue...  Brake Shudder / Judder 

Common issue noted by many riders not just ST4s, not just Ducati but, this is an issue noted on several Ducati forums (Ducati.ms (https://www.ducati.ms/forums/40-sport-touring/2151-brake-chatter.html) and DucatiSportingClub.com http://www.ducatisportingclub.com/showthread.php?t=25990)  So I opted to try the Ducati PN 69922861A - UNION+WASHERS KIT MTS03 Brembo banjo bolt.



11th Issue...  Neutral Switch Failure 

Another common issue noted by many Ducati riders (ST4s) included is the intermittent and eventual failure of the neutral switch aka gear switch, Ducati PN 539.1.021.1A.  In the photo below you can see where the plunger that makes contact in the gearbox to complete a path to ground when in neutral is worn down.


Old switch on left, new one on right.


Cut away view of the worn switch



ST4s 2002 USA Parts Diagram: click link for pdf