I performed the Desmo service on my Ducati Monster 797, and my valve clearances were very good, meaning they were all correct according to the workshop manual. I aligned the crankshaft to the TDC position and marked it. Then, I installed the new timing belts and bearings, making sure that I didn't disturb my marks. The spark plugs were replaced. The air filter was cleaned and oiled (K&N KU8015). I manually turned the crank 6 times, and I didn't encounter any scraping or sticking. Then, I set it to TDC 3 more times, and on the third time, the marks were aligned. Before this, I had a slight issue, but now it has become a bit more noticeable. The issue is as follows: When I first start the bike, the idle is normal, there's no issue while riding, and there are no problems with acceleration or top speed. However, when I stop at a red light, there's a shaking that feels like the bike might stall. This issue also occurs at idle. Sometimes, it disappears after a few hours. For example, the problematic engine behavior videos: https://www.youtube.com/shorts/URTJ5vjVcQE Sometimes, it runs perfectly: https://www.youtube.com/shorts/BUwRznJkixM The issue started here: I bought this bike around 10,000 km and have had it for about 40,000 km now. The first Desmo service was done at the shop, and since I didn't see any issues with the valve clearances, I did the second one myself. However, the issue actually started before I did the Desmo service. There's no error in the ECU, but there were 1-2 fuel sensor errors, which I cleared, and the error didn't come back. I suspect it might have been caused by bad fuel, as the problem was worse before—I could feel it was about to stall when I gave the throttle, and it stalled a few times at red lights. My quick reaction was to try Motul's fuel cleaner, so I added it to the new fuel on top of the old one, and the stalling issue at red lights was solved. However, the idle fluctuation still persists. If I remove the air filter cover, the issue seems to go away, even though the filter is clean, and there is sufficient airflow. The ignition is working, and the spark plugs are firing correctly. Now, I can't think of anything else. I plan to measure whether the ignition coils are supplying the correct energy, as it could be causing the idle irregularity when releasing the throttle due to insufficient energy. I'm using DCPR8E IX iridium spark plugs. I also tried the nickel ones, and the issue is the same. I think the belt frequencies are correct. The workshop manual indicated 140 +5, and I believe I was able to get a range between 138-142. I may have over-tightened them a bit; I wasn't able to get the exact data. I'll check the belt tension again, but my marks seem to be correct. I forgot to mention: The spark plug in the cylinder head has carbon buildup, just carbon buildup. There’s no oil or other substances. This makes me think there’s an issue with the fuel-air mixture, which further strengthens my theory about bad fuel. Thank you..
Presumably you plugged the bike into a diagnostic computer of some sort in order to see the errors. When it reported fuel sensor error what code did it give? The poor running sounds like a possible MAP sensor issue causing the ECU not to know how much fuel to dose. 140hz seems too high a belt tension, usually, depending on the belts, it’s 99-110 for new belts. However, I don’t think that’s the cause of your issue here.
Hello, thank you very much for your response. P0462 Fuel Level Sensor [short circuit to ground] P0463 Fuel Level Sensor Circuit high input I increased the belt tension to 140Hz because that's what was written in the manual. also thinking that it might be a factor. I was able to torque the spark plug on the horizontal cylinder, but for the vertical cylinder, the torque wrench didn't fit, so I tightened it by hand, ensuring it wasn't too tight. Could this be a contributing factor? I'll try tightening it a bit more tomorrow.
Fuel level sensor issues won’t affect the running of the engine, they’ll only affect the display on the dash of how much fuel is left and the consumption calculation. Spark plugs are usually, assuming they’re brand new and the sealing washer hasn’t already been crushed, just cinched down then given a further 1/4 turn, I can’t think I’ve ever used a torque wrench on them. If you lift the plug cap you’ll soon see if you’ve had blow by. I’m intrigued as to where in the workshop, or owners, manual it states 140Hz for the belt tension. However, I don’t think that’s the cause of your lumpy idling, belts set at that tension may just cause premature wearing of the idler & tensioner bearings. One of your cylinders is running too rich IMO as evidenced by the sooty plug and the fact the engine idles better with the airbox lid removed, ie, more air getting through. What diagnostic tool did you use? Im still veering towards a failed, or failing, MAP sensor.
Hey again, thanks for your reply! The horizontal cylinder's spark plug was sooty when I checked it. I used Melcodiag for diagnostics. I bought the workshop manual for the 797, and it states that there: I also suspect the MAP sensor. Could the battery be a factor? I noticed some slight bends on the terminals, and I’m using a lithium battery. A GPS tracker drained it a couple of times—could this be affecting efficient power delivery? Would unplugging the MAP sensor and checking for any changes help me determine the issue? Thanks!
https://ibb.co/fdYPSxc7 This is the information provided in the 797 workshop manual. Should I loosen it a bit more? I didn’t get Gates belts; I bought a Dayco set instead.
Hey, today I fiddled with the sockets a bit and simply sprayed some electronic cleaner. It seems to be working fine for now. In a few days, I'll take everything apart for a thorough cleaning, including the throttle body. I believe the issue is dirt and oxidation, but since I'm not sure about the sensor, I'll clean everything. Most likely, as you mentioned, it's the MAP sensor, so I'll focus on that first. https://www.youtube.com/shorts/Hh4izB2GoY0 https://www.youtube.com/shorts/TPihdNAdwj0 If I'm available tomorrow, I'll reduce the belt tension to around 120. When I measured before removing the ones installed by the service, it was around 125, so I'll adjust it to the same values. I'll keep you updated—really appreciate it, thanks a lot!
Well, it seems from Nelly’s response in the other thread 140Hz is what’s in the workshop manual. I’ll admit I’ve only ever used the ‘Allen key’ method on Desmodue engines as it’s simple, easy and effective, I’ve never actually measured the frequency. Anyway, your battery having gone flat won’t affect the idling issue of the engine. The battery is really only necessary to start the bike and to power the electrics whilst the engine is off but the dash is turned on. As long as the charging system is working correctly the bike, once running, is using the electricity generated by the stator. There is a way to test a MAP sensor which involves measuring its resistance change at atmospheric pressure and again when a vacuum is applied ie attach a plastic tube and suck on it. Acceptable values should be in the workshop manual. Alternatively, and I haven’t used MelcoDiag for a long time, perhaps MelcoDiag shows what pressure is being read by the MAP sensor and that which is being read by the atmospheric air pressure sensor. They should be the same. The ECU knows how much fuel to dose based upon the difference between the readings (voltage) from the map sensor and atmospheric pressure.
Hi, it seems that applying the Allen key method for the belts will be safer, as you suggested. I didn't actually see any test related to the MAP sensor in Melco, so I think it would be beneficial to clean it and observe any changes. Yesterday, when I simply cleaned the sockets, I noticed quite a difference, so I think I'm on the right track. Thank you.
When I unplugged the MAP sensor socket, the engine started running perfectly as it should. However, when I plugged it back in, the issue returned. I cleaned it, but it didn’t fix the problem. I believe the issue is entirely with the MAP sensor. I asked the dealer for a price for the socket. The MAP sensor is kaput hehe
It'd be interesting to know what frequency you measure as a check if you use the 5mm-Allen key method.
Actually, the 5mm Allen key was a tight fit, but I adjusted it so that a 6mm wouldn't pass. Then, I tried to match the frequency bit by bit using Continental's software. The same was the case with the belt the service had installed previously. I managed to reach around 140 with this method
I contacted the dealer for the MAP sensor, and I hope they have it in stock. Otherwise, they will have to wait about a month for delivery, though that is an optimistic estimate, and it could take longer. The sensor is BOSCH 0 261 230 287, which is also found in some Opel and Ford models. I will contact the Ford and Opel parts dealers. Do you know of any compatible products for the MAP sensor?
is there only 1 MAP sensor that services both cylinders? if its only one, shouldnt it affect both cylinders regarding over fueling? if its one for each cylinder, then yes, it could be the culprit.
It appears as a single unit on Ducati-Parts. When removed, everything runs fine; when reinstalled, the shaking returns. Sensor Installed: https://www.youtube.com/shorts/P3hTa01P1Fw Sensor Removed: https://www.youtube.com/shorts/8_FjXjF1kG4 The check engine light came on because I removed the sensor.
I just think its a bit weird it only affect 1 cylinder.. and maybe it is affecting both, and you cant really see the diff in the spark plugs. food for thought.. cant hurt replacing it anyway.. let us know.
Probably as you said, the tip of the horizontal cylinder's spark plug caught my attention, and I thought it was affecting only one cylinder. It’s worth observing again after the replacement. I hope the dealer can get it quickly. In Turkey, the dealer sometimes delivers the part in 10 days, but other times, it can take a ridiculous 2-3 months.
Yes, just the single MAP sensor as there’s only a single manifold from the air box to the cylinders. It’s a £40 part, may as well order it from Ducati, it will come with a 2 year warranty. It’s not worth trying to save a few €£$ in my opinion.
Actually, it's not so much about saving money in dollars, but rather my doubt about the Ducati dealer's order speed. Usually, my parts have arrived from Italy within 10-20 days, but recently, a few friends had to wait quite a while—one even waited 45 days. It's tragic but kind of funny.
It does depend what the parts are and whether they’re on back order at the factory or not. You could always try someone like StarTwin in NL, they’ve managed to get parts to me in 2-3 days that would have taken 10-14 days through the supply chain to here in Ireland.
