748 "Hiccup" issue at low RPM

[accludetuner]

So I've noticed my bike doesn't like low RPM or cruising at a constant speed. That's what I expected when I bought it so no issues there.

The problem is that every once-in-a-while the motor will "hiccup" at around 2500-2800 RPM. I was a mechanic and engine tuner for 10+ years before I joined the military so I know motors and basic mechanical crap and I don't know how else to describe it other than a "hiccup." It almost sounds like the motor is trying to ingest a valve, but it only does it once and then goes right back to running like normal. The sound of the "hiccup" seems to be coming from the front cylinder head but it's tough to single out because it only happens when I'm riding at those constant speeds.

It seems to do it when you're cruising at lower RPMs (2500-2800) at a constant speed but then ever so slightly increase or decrease throttle.....like you're cruising at a constant speed, constant RPM of say 2700 and then you slightly increase throttle to get it up to 2800 RPM, it will "hiccup" once and then work normal as if nothing ever happened. Idle and high RPMs are not affected by this issue.  Sweeping through the 1K- 4K RPM range it does fine....it only happens occasionally and only during the conditions I described above, but even then it doesn't always do it when in those conditions.


That's about the best description of the problem I can give. Anyone have a similar issue or know what this is before I start dissecting this thing to try to figure it out?

[J5]

quite normal

solution either ride faster  [moto]

or lower gear 3-4K + on the tacho

[booger]

I would disagree that it's normal. Doesn't mean a lot of owners don't live with the same problem, but I wouldn't say it's normal. The Ducati twins' natural proper state of operation is supposed to be smooth, with no coughs or sputters anywhere at any time. Lazy minded people will tell you it's the nature of the beast but I say that's nonsense, if the engine's in a proper state of tune you won't get any wonky behavior from it.
That said I had a problem pretty much exactly like that. Cruising around town, steady @ around 2800 or so down low, after a while at those revs I'd get a cough through the airbox every now and then. It got to the point where I could replicate it pretty easily. Other than that the bike ran OK.

A valve adjustment and subsequent tuneup cured my issue, but that symptom can literally be anything. You didn't explain what state of tune the bike was in, but instead of saying that Ducatis don't like to be ridden 'down low', which is nonsense, I'd say Ducatis don't like to not be in an even state of tune. You can ride them when they are out of tune, perhaps with no resultant harm, but they don't like it and will make sure you don't like it either. That stuff they say about Ducs being high maintenance is true.

My point isn't that you have to tear the bike down and go on an epic mission to perfect it. My point is coughing and sputtering at sustained low RPM riding is not normal. It is indicative of an issue. May not be a nuclear emergency, but it might annoy you enough to want to get to the bottom of it before too long. 

[accludetuner]

bergdoerfer - fantastic input!

Maybe the first 2 sentences gave the wrong impression.... it might be the smallest CC superbike for it's time, but it's still a superbike and they were designed for speed at the track. putting along at 20-30 mph for extended periods of time was not a priority in its' design. Even still, it shouldn't have the "hiccup" issue I described. That's kinda more what I meant.

As for state of tune - it's all stock minus a full V&H exhaust. It's due for the 12k maintenance which I will be doing myself soon and actually going slightly above and beyond the recommended stuff while I'm at it. Hopefully that takes care of the issue. I'll post back the results.

[brad black]

closing valve clearances
belt tension
tps baseline
throttle balance
idle mixture
eprom mapping

[accludetuner]

^ all of that was going to be done during the 12k maintenance except for the EPROM mapping.

As for the EPROM mapping, I want to hack and tune my own ECU which will come in the near future. For the time being, I was simply going to use the built-in potentiometer on the ECU to try to get it the best I could adjusting only the pulse. I've tuned cars, but never a bike. I've always used EGTs and LAMBA (wideband) sensors for the tuning but everything I've read says to use a CO tester for tuning the bike, not the LAMBDA. I was going to approach the tuning like I have in the past but I want to verify that tuning with the LAMBDA and EGT will be fine. I'd rather not buy the CO tester if I don't have to. Anyone know for sure if that'll be OK?

[booger]

For clarification, I was referring to the general state of maintenance when I used the term tune, not the particular exhaust/intake/ECU etc. Apologies for the confusion.

If you make sure all the valves are right on, dial the cams in, TB sync, and make sure your electricals are good, etc. that bike can be as streetable as any.

[accludetuner]

OK. I will take care of the 12k maintenance. Even without the scheduled maint, issues like this give me a legitimate reason to rip it apart and learn the bike better.

[accludetuner]

Bike has still been doing the "hiccup" thing since I made the original post.......BUT I think I solved it today!

The bike has gradually been idling rougher and rougher to the point that it started stalling out at stoplights. The worse the idle became, the worse the "hiccup" issue became. Obviously something wasn't right.

After checking the mechanical idler screw and some other common and obvious things, the problem didn't go away. So today, I popped the circular cover off of the ECU and adjusted the injector duration via the potentiometer inside the casing. You're SUPPOSED to use a CO2 meter to adjust it properly, but I just adjusted it by the sound of the idle and the smell of the exhaust. I ended up only needing to turn it about 1/64th of a turn couterclockwise....hardly anything at all. Magically, it idles fine and has not done the "hiccup" issue since. On top of that, throttle response seems more consistent and the bike just seems to have more pep throughout the RPM range.

I'll keep you posted if the problem crops up again, but this seems to have taken care of it for now. Thought I'd share my success for anyone else with this issue.

[supertjeduc]

If it returns , you could try to clean the injectors
I has the same problem and used some injector cleaning
Fluid and it helped

[accludetuner]

Been a month since I did it, put about 1,500 miles on it and it hasn't returned. I tried the injector cleaner and seafoam thing a few months back and it didn't help. Seems good to go now.