It's poppin'.

[BWClark]

...and I'm not talking about my lip-gloss.

I went out to my 2001 M900Sie with 6400kms the other morning to ride to a meeting, and started it up to find it popping and stuttering running a little rough. It was slightly more pronounced when cold, but was still obvious when warm. I rode it to the meeting anyway, and found it down on torque and power when pulling away from a stop. It could easily stall with a slight "pop" from the airbox. Under constant throttle at less than 6k rpms the bike would stutter. WOT it seemed to rev okay, but probably down on power.

What seems weird is that it literally happened overnight. The night before, I rode around without any difficulty. I moved the bike to our new apartment, parked outside for the first time, and the bike gets sick after a night out in the cold. I also thought it might be condensation/water issues, as the oil sight-glass looks "milky", but warming the bike up didn't affect the issue dramatically.

I went back to a stock airfilter a few hundred (500?) kms ago. The bike came with a K&N and a chopped box lid, but I didn't like the sound, so went back to stock. I suspect it might be running a little rich as a result, and the plugs are gummy. I haven't turned a wrench on any bike yet, so I thought I'd throw out the symptoms and get some moral support. Am I looking in the right direction?

I'd like to do an exhaust mod at some stage. I'll probably core them myself. Will this likely remedy any A/F mixture problem, if this is what I'm having?

Thanks,

BW   

[Buckethead]

How many miles so far this season? Has it been sitting for a while?

[BWClark]

Not sitting for any extended period. It's heading into winter here in NZ, and we've had a few weeks of rain when I didn't ride it at all, but it's always started right up no probs. I've been doing more shorter trips recently too, when the bike doesn't get as much of a chance to stretch its legs.

Edit: I want to add that the "popping" isn't backfiring. To my ears it sounds like it's a cough from the airbox.

[clubhousemotorsports]

sounds like it is lean to me. easy to find out just put the open airbox lid back on and see if it gets better.
Richening it up as you did when you installed the closed airbox lid should not cause the bike to pop in the intake. Loss of power I could understand but it should have made it richer.
Did your idle drop with the closed cover?

If it gets better with the open lid then I am an idiot and the bike is too rich. It can be leaned a bit to make it so you can run the closed cover.
could there be a bit of water in the fuel?

You say it is getting colder as well cold weather will lean out the mixture but the fuel injection should compensate some. The sight glass will get milky when it is cold no biggie.
good luck

[Ducatista]

Not sitting for any extended period. It's heading into winter here in NZ, and we've had a few weeks of rain when I didn't ride it at all, but it's always started right up no probs. I've been doing more shorter trips recently too, when the bike doesn't get as much of a chance to stretch its legs.

Edit: I want to add that the "popping" isn't backfiring. To my ears it sounds like it's a cough from the airbox.

I get the cough every once in awhile, too.  Basically one of the cylinders doesn't fire just right and cuts out for a split second.  What do your plugs look like?  How old are they?  How old are your coils?  Are they still stock?  What's the condition of your battery wires, terminals, and all those connections?  It doesn't sound like a "lean" issue to me, since I know what you're talking about when you say the "cough" coming from the intake as opposed to the bang coming from the pipe.

[Yoda9]

I have a similar problem on my 2001 M900i.e. Dark.  It runs fine below 4k and above 5k, but between 4k-5k, I get a "popping" sound from the airbox and the bike hesitates a bit.  I thought that the bike might be running lean, but I still have my stock airbox and am only running slip-ons.  I had someone suggest that it may be a problem with the  TPS...   

[clubhousemotorsports]

Too lean a TPS setting will cause a lean backfire in the airbox (sounds like spit-back).
It can be a poorly set up fuel injection or that the bike was mapped just right ... before the  ethanol was added to our fuel leaning things out.

[johnster]

Too lean a TPS setting will cause a lean backfire in the airbox (sounds like spit-back).

A lot of us have this problem...    I call it the airbox "sneeze"....

I've personally just been living with it and haven't done anything to fix it, cuz it doesn't do it frequently enough to really annoy me...  but it's a nuisance for sure... 
-It usually happens when I roll on the throttle between 2.5-3.5k rpm, and I'm like "OK, wtf was that!?!?!"...Then the bike continues to run fine, and I forget about it...

[clubhousemotorsports]

Some times it showes itself when on a long decel as well. It all depends on what the base map in the ecu is like. If it is borderline lean then when you add a low tps or a lean fuel (ethanol) these things show up. A good EFI set-up usually will take care of the problem.

[BWClark]

The "too lean" diagnosis is interesting.

I'm all academic in my knowledge. I haven't gotten my hands dirty much at all, but my take on *my issue* is in line with Ducatista's synopsis = spark problems. I haven't even pulled the plugs yet, and it'll be interesting to see if they're gunky. I'm thinking the plugs/wires/coils route...

I was under the impression that a lean mixture will still burn quite well, and is more likely to result in overheating and loss of power before any stuttering...   

[clubhousemotorsports]

Too lean a condition can cause a misfire which is what you are hearing. A lean misfire can also miss-lead you by giving you high CO readings because the charge that finally ignited did not all burn.

[Howie]

The "too lean" diagnosis is interesting.

I'm all academic in my knowledge. I haven't gotten my hands dirty much at all, but my take on *my issue* is in line with Ducatista's synopsis = spark problems. I haven't even pulled the plugs yet, and it'll be interesting to see if they're gunky. I'm thinking the plugs/wires/coils route...

I was under the impression that a lean mixture will still burn quite well, and is more likely to result in overheating and loss of power before any stuttering...   

Lean burns well.  Too lean causes lean missfire.  Too lean can also cause popping.