Strange clunk at 3K RPM on 996 Bip

neilma · 10 Jul 10, 06:51 PM

Hi to all on my first post! (Disappointed its asking for help though so apologies!)

Recently purchased a 996 Bip and noticed an issue with it.

If I ride along at around 3000 RPM, the bike will occasionally act like a misfire, jolt slightly, and make a metallic clank noise. I first thought it was the clutch as all the plates were well worn as was the basket so I have just replaced all the plates, the basket and for good measure got a new slave and push road and the problem still occurs.

I can repro it if I cruise at around 3K and then quickly open and shut the throttle or as I say it will do it when on a constant throttle but always around 3K.

Is it misfiring? Anything else I can check as I am a bit confused?

Other than that, the bike runs fine (although it sometimes stalls if its not warmed up but not sure if thats related).

Thanks in advance

Neil

The Dieselinator · 10 Jul 10, 07:47 PM

My thought is that the 996 doesn't really like being run at a lowly 3k. It has got twin injectors which don't function well at low revs, so that may well be it.

Douglas · 10 Jul 10, 07:54 PM

Quote:

Originally Posted by The Dieselinator

My thought is that the 996 doesn't really like being run at a lowly 3k. It has got twin injectors which don't function well at low revs, so that may well be it.

I was thinking the same thing Pete!

I wouldnt change up until the engine will pull 4.5 in the higher gear, and see if all is well then.

Mr.R · 10 Jul 10, 09:33 PM

As the other lads have said you're trying to ride a sports bike like a Hardley Worthitson.
Many years ago (getting on for 30 years now) I built a tuned 900SS Bevel for a customer who came back complaining about the same problem as you...
I took it out for a ride and couldn't find a problem, I then asked him when it was happening and what bike had he rode before???
He was a BWM boxer twin owner and was trying to ride a sports/race tuned bike in the same way.
I've owned Desmoquatros for over 11 years, (Ducati's for well over 30 years now) wouldn't dream of letting the revs fall below 4000 rpm on a very gentle throttle and wouldn't snap it open anything under 6000 revs.
If you want to pootle around buy a Hardley or a Beemer, you're killing the Ducati by riding it that slowly/at those low revs mate.
You've got to learn how to ride it/adjust your riding style or sell the bike and buy a cruiser.

Steve R

DukeDesmo · 10 Jul 10, 09:48 PM

As above, could just be a low rev 'lumpiness', my 916 does it around the 2.5k mark but clears by 3k, but 996 have longer final drive ratio as well as bigger pistons and the dual injectors are not so good at low revs so maybe not so smooth low down?

Otherwise check your flywheel nut's not loose.

Dunbar · 11 Jul 10, 12:47 AM

Had any new tyres lately? Check the back wheel's on properly!

I had a similar 'misfire/stutter' that kicked/jolted slightly thru the drivetrain at about 3k. It started after I swapped back to std cans and had some new tyres put on. Thought it was a fuelling issue due to the std cans and still being chipped for the 50's.

Long story short, turns out the tyre guy (a reputable co with alleged bike specialists) had not located my rear wheel properly after he'd fitted the rear tyre. Wotta spunt!

5 spoke Marche's as per 996 CAN be put on wrong and not be located on the pins correctly.

Justa fort...

neilma · 11 Jul 10, 09:25 PM

Thanks Chaps. As it happens I had replaced a tire recently (but it was clunking before then). I'm not sure i'd put this down to how its being ridden as I have ridden many twins before and still own a Tuono so I recognise when its a bit lumpy at low revs. This is definately not a normal sounding noise.

I will check the flywheel nut so thanks for the pointer.

I had seen some posts about disabling one of the injectors - is that a quick thing that is easily reversable to try or does it mean getting it chipped etc?

Thx again
N

VMT 500 · 11 Jul 10, 11:59 PM

Is the "metallic clunk noise" transmission snatch ?
(the same as you get at low rpm in traffic etc.)

What gearing are you running ? My 916 is much improved with 14t front sprocket.

Can't comment on why the misfire, altho' mine occasionally misses a beat.
(.....they all do that,Sir...? )

...and yes, I can coax mine in favourable conditions from 3 grand, but don't introduce
power 'til after 4000....wind it on after 5......but never "quickly open the throttle"...
& that's with lower gearing.

Pilot error ?

Kriis · 12 Jul 10, 04:10 AM

as above, your bike transmission will produce quite an audible 'clack' 'clack' 'clack' if you ask too much of it in too high a gear at sub 3k. I can only speak for myself, but happens occasionally in traffic if I get caught out in the wrong gear. (and particularly if i'm tired!)

neilma · 12 Jul 10, 11:17 AM

Hmm thats the thing, this isnt a clack clack like sound (although I know exactly what you are saying as it has happened to me in the same circumstances)

This is like ummm... when you get a stone fly up and hit your windscreen - More like a loud crack sound and it doesnt do it all the time....
(Oh and running 14T at the front).....

stevel · 12 Jul 10, 12:02 PM

There's a well known misfire on some of these at 3500rpm caused by the dual injectors not working effectively, but your symptoms don't sound like that. There are mods to disable one, but you need a new chip and set up.

You may have a slightly weak mixture, that can cause occasional spitting back into the airbox......my experience of that is best described as a "sneeze" sound with a dull thud felt through the throttle grip. You can measure it by getting the CO in the exhaust gas checked, you need around 4 to 5% for good running, but they are sometimes set at less to comply with Environmental regs. Do you know when that was last done, poss try a CO reading if you can get access to the kit or a garage will do it.
Adjustment is usually a step in the full set up of the throttles and balance etc, but you can effect a change by tweaking the idle pot on the ecu board. Try a search on here as the set up and other info is well covered

They don't like low speed chugging as has been said, but if set up properly my 996 will pull cleanly from very low, but everything needs to be blob on! (And I'd agree that you shouldn't ride that way as the norm)

Kriis · 13 Jul 10, 09:56 AM

Quote:

Originally Posted by neilma

This is like ummm... when you get a stone fly up and hit your windscreen - More like a loud crack sound and it doesnt do it all the time....

now you've spelt it out, I see what you mean and i would be concerned too.

boots · 13 Jul 10, 10:45 AM

not a loose drive chain perhaps slapping.

749si · 13 Jul 10, 11:43 AM

Might sound a bit extreme but have you checked the frame for any cracks around where the sound is coming from, does it happen when genearl riding or under braking or acceleration ?, just a thought given the description of the noise

DukeDesmo · 13 Jul 10, 10:47 PM

Quote:

Originally Posted by neilma

This is like ummm... when you get a stone fly up and hit your windscreen - More like a loud crack sound and it doesnt do it all the time....

Lean mixture backfire through one of the throttle bodies maybe? Are any or both of the throttle bodies 'blackened' with soot? Are there any air leaks (splits) in the intake manifolds?