[qdot]

Hey guys,

I recently went on a trip from Sydney to Melbourne, and on the second day I first noticed some terrible stumbling issues when in either 5th or 6th gear, rolling on from around 3500-4000rpm. At first, I thought it was bad fuel and tried my best to run it down and dilute it with more petrol whenever I had the chance. It then turned into a very bad misfire when getting off from standstill in the CBD, with a very rough idle that would occasionally drop and spike in revs. Babied her to the Melbourne Ducati Dealership who took one look at it and said it was a big end. Being forever skeptical of shitty mechanics in Australia, I elected to ship her home.

Due to fueling up in a small country town, I naturally assumed it was a fuel related problem, and went through all of my fuel delivery system; injectors, filter and pump. Alas, that was not the problem. When doing more testing on the ignition side of the problems, I took both spark plugs out and turned the engine over with the spark plugs on the engine casing, and noticed that every now and then, there would be no spark on both spark plugs even though the engine was turning. The fact that the spark plugs didn't fire on the same rotation of the crankshaft pushed me away from suspecting the coils of failing, as it was very unlikely that they'd both fail together. I'd also switched the leads and plugs around to make sure that the problem was still here. This led me onto checking the timing sensor on the left side of the engine, and although I don't have the correct feeler gauges, I just tried how the engine would run with different air gaps (as the bike originally had two shims put together), but it made no difference and so I replaced timing sensor today, and it still misfires.
I was also pretty confident in replacing the timing sensor would be the solution to the problem, as it states in the Haynes Manual that the sensor should have 680 ohms resistance, and I was measuring just over 900 ohms. However, when I picked up the new sensor from Ducati today and tested it in the car, it was reading around 930 ohms.

I'm starting to claw at every small problem now, as I could only think that the timing sensor being faulty could cause the ECU to not fire the spark plugs, due to not getting the signal. I have also removed everything additional and not necessary on the motorcycle, such as the Power Commander and Healtech Quick Shifter.. Probably about to go through testing all of the engine management relays, and maybe double check my regulator rectifier is working properly when I have more time another day as I could swear that my bike previously had a higher voltage at idle..

Any help or suggestions would be amazing.
Thanks in advance guys!

 

[belter]

do you know it's not a run big end? check the oil pressure - if it's got about 45 psi and rapping wildly, it's rooted. not always immediately obvious.

a roll on misfire at 3,500 rpm where it goes "duh duh duh duh duh vroooooooomm" is a specific 996 thing. some reading on it here - http://www.bikeboy.org/996stradaum222eprom.html - but really single injector eprom or (preferrably in any case) reducing the closing clearances helps massively.

is the fuel pressure good? battery charge voltage? throttle body balance? idle mixture?

 

[qdot]

do you know it's not a run big end? check the oil pressure - if it's got about 45 psi and rapping wildly, it's rooted. not always immediately obvious.

a roll on misfire at 3,500 rpm where it goes "duh duh duh duh duh vroooooooomm" is a specific 996 thing. some reading on it here - http://www.bikeboy.org/996stradaum222eprom.html - but really single injector eprom or (preferrably in any case) reducing the closing clearances helps massively.

is the fuel pressure good? battery charge voltage? throttle body balance? idle mixture?

From everyone that I've talked to, if I really had done a big end, they say that it'd run like an absolute pig. I managed to ride 400km to Melbourne, and it still goes around the streets just okay at the moment. I don't have a tool for checking oil pressure, but I did check cylinder compression the other day and it was 150psi for both cylinders. Nor do I have a tool for checking fuel pressure. I also haven't touched the idle mixture in the ECU.

My 996 has already had the single injector modification done to it, and therefore it can't be the problem that the 222 Eprom can fix..
The roll-on problem was just the first sign that I experienced of something not quite right. As I mentioned above, when I have both of the spark plugs out of the engine but still attached and turn the engine over, it is very obvious that the spark plugs are missing firing intervals. We all know the firing sequence that a V-twin engine makes, and you can see it in the way the spark plugs fire. When you hold down the starter for around five seconds, you can see that the plugs don't fire every now and then, and when they don't fire, both plugs skip it at the same time.

I'm starting to think that the battery voltage may have something to do with it. Possibly not having enough voltage for the coils or something along the lines of that, especially after noticing that when the bike is on and idling, my voltage is slightly lower than what it used to be. However, my stator just got rewound by a specialist 6 months ago, along with a battery and regulator rectifier. It also stumps me as even when the stator had failed, I still managed a track day at Sydney Motorsport Park with no charging system, and the bike worked perfectly.

 

[bbradsby]

Perhaps look at these: intermittent spark could indicate a loose ground somewhere such as the ECU-to-engine; intermittent kill switch or side stand switch due to corrosion from weather exposure over time; poor conductivity in the secondary wiring. Or ultimately perhaps a weak ECU. due to the age of the 996 series, quite a few bits to investigate.

For fuel pressure, rent a gauge fro auto parts shop, lift tank, and patch it into the supply line upstream from the first injector in line.

 

[WileECoyote]

I had a misfire on mine. Put Seafoam in the tank and ran it hard. Turned out to be something in the injectors as it cleaned up and pulled hard.
Start with simple stuff first before you get too deep and possibly look over an easy fix. Best o luck.

 

[bbradsby]

^ what he said.

However, do understand that the bike is almost 20 years old.. so electrical gremlins start to creep into the works, and checking the resistance, continuity, voltage readings is pretty simple. Also, switching out the two relays under the seat and the water temp sensors on left side of engine are two quick experiments that, along with the side stand switch bypass, are known issues and can be done on the side of the road. Each of these can potentially get you home.