BMW R1200R R1150R/T F800 K1200R R1100R/T R1250R RnineT Message Board

Hi guys-
Every once in a while and it almost seems slightly random ( as in one in a dozen times) when starting the bike I hear a 'pop' or 'crack!' Only when the bike is at temp, I don't recall it happening when starting cold. It sounds electrical in nature and also 'seems' to come from the front right. When I say electrical what I mean is instead of a more mechanical sounding 'thud' or 'clunk' it has that unique arcing sound that is hard to replicate. Of course I could be totally wrong as when it happens I'm not expecting it and in a millisecond, it's gone.

I've tried to do a couple of things to try and isolate it but have been so far unsuccessful. 1. starting the bike after it's warm and kneeling down in the area I think it's coming from and 2 giving a quick look at the alternator (which was replaced by the PO.) while starting starting the bike and looking for some kind of signs, but because of it's randomness it hasn't shown it's face again in those attempts.

Wondering if this rings any bells with anyone or if anyone has thoughts as to how to narrow my search to be able to investigate it further?

And lastly I just received my plug pulling tool so will give a look there as well when time permits.

And really lastly I know that this is like my wife bringing the car to the mechanic telling them that it was making this funny sound a few days ago and isn't at the moment, but when it did it sounded like 'grrrrwizzzclunkclunkgrrr' "whadayathink it is"?

Following this with interest. I have a 2004 that doesn't do this, but earlier this year I was working for several months in CA and was loaned a 2002 model for a couple of months, and that bike did that. I interpreted it as a combustion thing, it happened only sometimes, and didn't seem to really affect anything, but it was quite concerning to me since it was a loaner bike and I didn't want any problems with it. Hopefully, someone can enlighten us both on this.

Agree D it doesn't *seem* to affect anything, the bike starts right up, no hesitation or interruption to the process just this audible 'crack' or snap' sound. like I implied, it's one of those things that happens unexpectedly and very quickly so it's a little difficult to isolate what and where it comes from. My spider senses tell me that it's on the right side, but again it's so short lived that I could be wrong, and while I interpreted it as electrical I could very easily be wrong there too.

My California 02 “cracks” on occasion too. I never gave it too much thought. Bike still ran fine after the noise and I always thought it was sort of a “pre-ignition” snap because the engine was warm...vapor....etc. but I really don’t know.

My '04 and the '03 previous did what I suspect was the same thing. Only after a hot (90 degree day)run, cools down for maybe 15 min or so and then go to restart. I suspect a bit (at least in my case) of pre-ignition due to temperature.

Appreciate you guys weighing in. It could very well be a pre-ignition knock and I mistook it for being electrical as the sound is kind of unique that doesn't sound like anything similar. And Towerworker, those seem to be the exact conditions when it happens. Hot run, 90 degrees, short cool down, re-start--> knock!

And edited to add- that it makes the knock/pop/crack only once at start up, and only occasionally under those conditions. I've only owned the bike since May or so and it's been relatively hot air temps in that time. Haven't yet had a chance to see if it happens in the cooler weather.

My 2002 r1150r does the same thing once in a while. The only success I've had has been to disconnect the battery terminal leads and go over the contact surfaces with some steel wool then reconnect with some Vaseline like Dielectric grease. Then it will stop making that noise for a few weeks but eventually start up again. Maybe the terminal is too close to some other metallic surface and there's a spark jumping? I'm no engineer so I really have no idea if that makes sense or not. Maybe somebody else on the Forum would care to make a more educated comment?

Come to think of it, the bike used to make that noise a lot more when I first purchased it about 6 years ago. In fact there were a few times that I would stop the bike turn it off and then go to restart it and get absolutely nothing no lights no fuel pump no ignition. I had to remove the bolt that secures the AFT end of the gas tank pry it up a few inches and reach under to the battery contact and jiggle or move the contact a bit and then the bike would restart up fine. I don't know if this is related to that popping

Interesting S...My perception is that it's on the right side, but that's only a perception as I haven't been able to duplicate it when I'm looking for it. I plan on taking a look at the battery but probably not until later in the fall. I *think* everything is good under there as my bike came with a receipt/shop order for a battery replacement last year at the dealer...but honestly I haven't looked yet.

One thing though that goes along with my perception is that it seems to originate at a higher point than the cylinder head, but again I could be way off, it's so momentary. If it is electrical and it is an arcing sound, probably not a good idea to have it happening under the fuel tank my 'pop' could become a kaboom!

Knock can be one-sided or one-cylindered. My 2002 Roadster and '96 R850R both pinged at high temp/low speed/open throttle.

Pull the tank, look and sniff to put mind at ease about any electrical origin of sound.

For me the sound is like the sound of a whip cracking and it is always a single crack only while holding the starter button.

That’s a good description of the sound. Short and sharp cracking sound and only once which is why my inclination was electrical initially. I don’t really know what an engine knock sounds like but I’d guess it’s similar? And this is relatively loud and unmistakable that it’s happened.
I searched for a video to see if I could hear something similar but only found automotive examples and they were subtle by comparison.
And the same, only while I’m holding the starter button.

Photoguy wrote:...only while I’m holding the starter button.

Forget engine knock then, doubtful it would happen during starting.

Cam chain tensioner? Or one of the guides?
Something related to lower oil viscosity.
Noise associated with alternator/belt?

Thx Sweatmark, appreciate the input. One of my first thoughts was the alternator as it had been replaced with an aftermarket one by the P.O. and it seemed to be in the vicinity of the source of the sound, but of course when I took off the cover to try to duplicate it, it didn't happen.I thought that maybe he didn't tight a bolt or something, but that wasn't the awe. The sound is unique and as described above kind of like a whip cracking....and only on starting in the conditions others have described- hot day, short cool down then re-start. And of course it doesn't always do it so it's hard to duplicate it to try and isolate the source. Despite it so far only happening in those conditions, it's also random...it doesn't always do it.

For the time being I guess I'll take comfort in knowing that others have experienced it as well and so far at least there doesn't seem to be any consequences that are obvious.

Same thing happens with my 2002 RR and I attribute it to a backfire of fuel in the intake manifold. Sometimes it'll also run rough for a few seconds afterward but resumes purring as soon as I rev it some.

Good to know Sunmeemer. Don't really know what it is but at a minimum, I know I'm not crazy. Yet.

Starter motor engagement/disengagement? Solenoid for same?

That's a possibility gregor. The sound *seems* to come from the right front though (as best I can tell), and for lack of a better description, doesn't sound 'mechanical' if that makes any sense?

I had a starter go on me a couple years ago after it sounded like it was turning the engine over sluggishly for a few months beforehand, so I finally replaced the battery, which didn't help at all. Then one day at the post office it just went clunk when I tried to start it but wouldn't turn the motor over at all. It had made some minor grinding-kind of noises beforehand, but nothing real noticeable. I push-started it and replaced the starter at home. Someday I'm going to take that starter apart and see what failed, but I have a sneaky suspicion the metal plate in front of the armature came loose and jammed it.

Photoguy, get some better ear plugs and ride it.