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Discussion Starter · #1 ·
Hi all,

There seem to be a bunch of these threads but I have not been able to find one matching my symptoms, so here it goes.

I have a 13 848 with about 12k on it that seems to suffer from a weird low rpm stumble. When the bike is cold it seems to be running well however as soon as it warms up low rpm part throttle performance is poor. The bike stumbles and accelerating out of a corner or from a stop produces alot of vibration when below <4k. WOT performance seems to be ok.

I checked the plugs and they look ok, maybe a touch on the rich and the horizontal plug threads were wet.

The bike is new to me and generally seems to be well maintained from a mechanical perspective, the belts and timing were supposedly done already. The tank however shows signs of swelling.

Any ideas on common items to check? DucatiDiag seems like a worthwhile investment. Any suggestions would be great. THX

Tom
 

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Discussion Starter · #3 ·
The bike is new to me so afaik its stock gearing with stock ecu. Whats std/dp? I would assume once warmed up it's all closed loop.
 

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I’ve been giving my two cents worth on this sudden rash of riders worried about this. I rode my own Testa motored bike, an ‘07 S4RS, a couple of days ago and purposely lugged it a lot just to see what all the concern was about. The 2 valve motor smooths out about 3000-3500, the 4 valve about 4000-4500 and doesn’t like 3500 rpm at all. Is that what you’re experiencing ? Every engine seems to have a spot in the rpm band it doesn’t like, a spot where maybe timing or a/f ratio or engine balance is not ideal. Harley’s have a dip in the power band around 3500 rpm that tuners have been trying to minimize for 115 years now, so maybe it’s a trait of the engine configuration. I have noticed one thing that I’d forgotten though, my Ducatis run smoother on ethanol free fuel, both 2 valve or 4. Plus, I always run SeaFoam with the fuel. Maybe that helps. The main thing though, is I ride a Ducati like I would ride a two stroke. If you came from some other brand, maybe you have a riding style that exacerbates the rough spot in the power band. I’m not trying to give you a hard time, this is actually what I’d call a constructive dialog.
 

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Discussion Starter · #5 ·
All my experience was riding I4 bikes (600rr/s1000rr), both were pretty smooth regardless of the rpm band. I knew ducatis were a bit rougher and I have to say to make a smooth corner on the 848 I need to be going pretty fast. When making turns 2nd is too rough, it feels like the motor is lugging which upsets the balance in mid turn. The key is that when the bike is cold it rides so pretty smooth, it just seems like a tuning issue. I have a AFR gauge somewhere I need to dig up.

Is there an easy way to force the ecu into open mode?

Tom
 

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i rode one yesterday that was quite vibey. at idle on the gas analyser is was 0.5% co, which even for a closed loop ecu is quite lean. std is standard ecu, dp is ducati performance. get the ecu flashed to be open loop and maybe shorten the gearing a bit depending on what it is now. the one i rode yesterday felt quite long. std is 15/39 the manual says. i'd go 14 front for sure.
 

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Discussion Starter · #7 ·
The gearing seems ok, I really hate to mess with factory made stuff. I have the 5AM ecu which seems to offer up a bunch of opportunities. Just waiting for my cable to get here. Is there an easy way of forcing the ecu to stay in open loop? like faulting/unplugging a specific sensor? o2?
 

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I can tell you that with BMW 2 valve air cooled twins they all have a spot where they seem a bit rough it is normally in a range of about 400 rpm and can depending on the bike be anywhere from 2200 - 3800 rpm's-- nice and smooth under and above on my 77 R100SRS it starts right around 2800 and goes away completely by 3300 rpm. It just feels a bit rough and buzzy
 

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Discussion Starter · #9 ·
I have no doubt that other bikes run rougher or have spots where the tuning isnt great; What I care about is making my bike run better. From what I can tell compression is good, timing seems alright, valve clearance are within spec. I have a few more items to check but generally it looks very healthy. I will post a video after all the maintenance is done.

White running rough might be subjective I still think this bike should run smoother. Like I mentioned light throttle in mid turn make the bike choppy which upsets the balance and generally is very annoying, only happens once fully warmed up. When cold the bike rides like a dream. It all seems like a software/tuning issue which is something that can be changed fairly easily.

PS I have the 848 EVO DP ecu/tune.
 

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just spit balling here --have you checked for any air leaks? but this is of course speculating that the issue is fuel related, it could always be something else. could be engine management / fuel injection, throttle pot ---and is this something that just came up all of a sudden?
 

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Discussion Starter · #12 ·
the bike is new to me, came with this issue; at a decent discount :)

by throttle pot, do you mean the tps calibration or just the sensor going bad?

There doesnt appear to be too many spots for an air leak, basically there is only one coupler between the airbox and the engine inlet (the rubber boot at the throttle bodies) and that connection seems solid. I thought about unplugging the sensor sitting in the airbox, I assume this is a MAP sensor of some sort? Would that cause the ecu to go into open loop?

I am still waiting for cables from china so right now im trying to catch up on all the maintenance. At this point I flushed all the coolant, did plugs, belts, valve adjustment (didnt need any), fuel filter, checked fuel tank for evap line restriction, compression test everything looks tip top.

How common is it for ignition coils go bad on these things? The horizontal cyl plug was wet which makes me think that either the mixture is too rich or the plug isnt firing... I have had similar issues on cars with bad coils, under heavy load only when warm the car would misfire. Does the 5AM do misfire detection?

Thanks for your help
Tom
 

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Discussion Starter · #13 ·
one more quick question, the manual specified 650mili Ohm +-50 on the primary winding of the coil which is what confuses me, my coils are 3 wire. I thought the primary circuit is not accessible on these coils since in essence youd be measuring the transistor itself and not the coil.
 

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yes the throttle pot is the same as tps sensor, check it's adjustment make sure it's good --air leak could be between the throttle body's and the head where the rubber manifolds are-make sure that the clamps are tight and that there are no cracks in the rubber--easy check is start the bike and spray a little brake cleaner around the intake tract--if the idle gets faster or slower you have an air leak.As for coils that should be something really easy to diagnose, and if it is running fine at idle then has a stumble @ whatever RPM then clears up above that RPM I very much doubt a coil, but you never know --if you changed the plugs & plug wires and still have the issue --I'm not sure about this but someone will know for sure--If the coils are the same coil for each cylinder then you could swap the coils to see if the issue changes to the other cylinder--But this is ONLY if the 2 coils are the same part number and this I do not know
 

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Discussion Starter · #16 ·
The TPS is on my list, as soon as I get the cable. The throttle boots are ok since I just put that stuff back together. This is COP so no wires but the coils are the same. I put everything back together after redoing the timing and it runs about the same as before. I rode my buddies street glide (vtwin) and it doesn't exhibit any of these annoying issues...
 

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I listened to that and at the 2 places you said @ 1:41 & 2:14 I'm sorry that sounds like nothing more then you are lugging the engine I dont know what gear you were in at those 2 places but I would say downshift it --thats all it sounded like to me --But I am not a Ducati expert by any means--But if that were a BMW I'd downshift and roll it on. --and if My 900SS or 907ie sounded like that I'd do the same
 

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And remember that that Harley your talking about is not exactly a performance motorcycle --those things get lugged around all the time basically because they dont have a enough power to pull a greased string out of a cats ass, thats why they are so bloody slow. you have to keep in mind what each bike was built to do. your riding a Ducati Superbike----not a Harley garden tractor
 

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Discussion Starter · #20 ·
that was 1st and 2nd respectively, I guess ill just ride is around some more now that the maintenance is done. Thanks again for your feedback.
 
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