Unusual engine sound, video, r80

[marknreimer]

Hello,

First, I'm new to the forum, so hello everyone

I recently purchased a 1986 BMW r80 from a friend of mine who's had it for the last few years, maybe 3-5 years. I've been politely nagging him to sell it to me and he finally came around about a month or two ago. I've been going through the bike and making small repairs/updates (new brake rotors, cables, a few gaskets, springs/rear shock, changing all fluids, etc) but recently I started noticing an odd sound originating from the engine. It doesn't happen all the time, so it's been tricky to capture it on video.

I've done a few things to try and narrow down where this sound is coming from:

- It will happen when the bike is in neutral with the clutch released. It also will do it when in gear and the clutch pulled in, or when accelerating/decelerating with clutch released. In other words, when stationary, moving, clutch in or out, on the gas or off the gas. That suggests to me that the sound is not likely originating from the tranny since, if I understand correctly, nothing is moving in the tranny when the bike is not moving.

- The fact that the sound is consistent when the clutch lever is pulled in or when it is released suggests it likely is not a clutch issue, correct?

- So, moving forward along the engine, I'm thinking the sound could possibly be a rod bearing, or perhaps the timing chain? I've asked a more experienced airhead owner to come have a look later this week, but beyond that I'm on my own and stumped!

- For what it's worth, the bike runs perfectly other than this mystery sound. It idles steadily at 1050rpm, accelerates hard and smooth through the entire rpm range, fires up quickly, quite a joy to ride really. Odometer reads 20,500km, though with only five digits available I suppose I have no way of knowing if it's actually 20,500 or 120,500km. The bill of sale my friend received indicated he bought it with 7,500km on it, but I find that hard to believe based on the wear in some parts (IE: The rear drum lining is worn right to the maximum recommended level right now)


Here is a link to the video with the strange sound. Any thoughts? Thanks!

https://www.youtube.com/watch?v=MEtMKPZ1IlI&feature=youtu.be


Thanks everyone, I'm looking forward to learning a lot about these wonderful bikes here!

 

[20774]

Welcome to the forum! After listening a couple of times, I'm not sure I'm hearing anything unusual except for a low throated sound. That sounds seems to be something that is associated with the muffler, maybe a pinhole in it somewhere.

Maybe those with better hearing will step in.

 

[marknreimer]

Welcome to the forum! After listening a couple of times, I'm not sure I'm hearing anything unusual except for a low throated sound. That sounds seems to be something that is associated with the muffler, maybe a pinhole in it somewhere.

Maybe those with better hearing will step in.

Hi there, thanks for the welcome. It is indeed tough to hear it in this video. It occurs first at the 6-7 second mark as the engine slows down from the throttle blip, a kind of warbling (is that a word?) rubbing sound, and disappears when the engine returns to idle.

I'll try to get a better example this evening when I go for a ride. The notion of a leak in the exhaust is interesting though. I'll check the crossover pipe up front and the finned header nuts today.

 

[lkchris]

I'd initially vote exhaust system, too.

It's clearly been modified as the crossover can is no longer there.

In any event, sure don't think it's anything as serious as rod knock.

 

[marknreimer]

I'd initially vote exhaust system, too.

It's clearly been modified as the crossover can is no longer there.

In any event, sure don't think it's anything as serious as rod knock.

Yes, you are correct. There is a crossover pipe at the front right at the base of the 180-degree bend, but the rear collection box and crossover is gone entirely. Thanks for the advice, I'll check the exhaust and report if I discover anything.

 

[SCBuckeye]

"It will happen when the bike is in neutral with the clutch released. It also will do it when in gear and the clutch pulled in, or when accelerating/decelerating with clutch released. In other words, when stationary, moving, clutch in or out, on the gas or off the gas. That suggests to me that the sound is not likely originating from the tranny since, if I understand correctly, nothing is moving in the tranny when the bike is not moving."

Someone else may correct me if I am wrong, but when the bike is running and in neutral with the clutch released, the engine is turning the input shaft of the transmission. So..there is something in the tranny moving when bike is not rolling.

I would also check something, but does not fit all of your scenarios. The clutch throwout bearing could be running dry.

In theory, the throwout bearing should not turn when the clutch is not pulled in.

 

[marknreimer]

"It will happen when the bike is in neutral with the clutch released. It also will do it when in gear and the clutch pulled in, or when accelerating/decelerating with clutch released. In other words, when stationary, moving, clutch in or out, on the gas or off the gas. That suggests to me that the sound is not likely originating from the tranny since, if I understand correctly, nothing is moving in the tranny when the bike is not moving."

Someone else may correct me if I am wrong, but when the bike is running and in neutral with the clutch released, the engine is turning the input shaft of the transmission. So..there is something in the tranny moving when bike is not rolling.

I would also check something, but does not fit all of your scenarios. The clutch throwout bearing could be running dry.

In theory, the throwout bearing should not turn when the clutch is not pulled in.

Yeah I think you are correct on that. This morning while riding in to work the sound was louder than it has been lately. It's also a lot colder this morning (around freezing), who knows if it's related. Anyway, with the sound being louder, I was able to narrow down the location a bit. It's not coming from behind the front cover, but rather seems to be originating from around the breather under the starter cover. I'm pretty confident it isn't coming from the lower engine down by the tranny or the front by the timing chain. I picked up a mechanics stethoscope to narrow down even more, but regardless I will be taking a look under the starter cover and inside the airbox to see if anything is obviously amiss in there.

 

[guenner]

The 'klackery' sound in the video sounds to me like from the transmission. It should stop once you pull the clutch. If so, I was told by my master mechanic not to worry. It's an airhead 'thing'.

The other deeper sound seems to come from the exhaust. Check the connections for exhaust blowing out.

The motor seems to slow down slowly when the throttle is closed. Could be carbs out-of-sync.

Other than that, all I hear in the video is a nice airhead sound.

/Guenther

 

[marknreimer]

The 'klackery' sound in the video sounds to me like from the transmission. It should stop once you pull the clutch. If so, I was told by my master mechanic not to worry. It's an airhead 'thing'.

The other deeper sound seems to come from the exhaust. Check the connections for exhaust blowing out.

The motor seems to slow down slowly when the throttle is closed. Could be carbs out-of-sync.

Other than that, all I hear in the video is a nice airhead sound.

/Guenther

Thanks Guenther.

The sound I'm questioning is easily heard at 41-43 seconds in the video. Kind of a fluttering sound the slows and stops as the engine revs down to idle.

I don't notice any sounds changing with the clutch pulled in or released. The clacking sound in the video I believe is the valves. I don't recall hearing anything coming from the transmission, but I'll double check, and also look for any exhaust leaks again. The engine 'pops' while engine braking, which could possibly be due to an exhaust leak as well. However, I'm confident the sound I'm questioning is coming from inside the engine somewhere.

 

[pglaves]

I thnk it is the crankcase vent valve reacting to crankcase pressures.

 

[czbrat]

Noises

hey, I wrote in myself about noise from my r65 engine. Mine seems to come from the front of the engine.cam chain??? I listened to your video, and your bike sounds great. A friend says that we just forgot all the noises that bikes used to make. Good luck

 

[marknreimer]

Last night I finally got under the starter cover to investigate the breather. Everything looks brand new under there. And the bike is already fitted with the reed style breather. I removed and cleaned it, but it sure didn't need it. All the hoses were done up tightly, and they feel new as well, soft and supple. Have a look at the photo.

I understand this style breather is not known for the howling noise, meaning the noise shouldn't be coming from here..

It was suggested to me that it could be a worn timing chain. If so, I'll be keeping an ear open for any changes, but continue to ride as-is for the time being. Riding season is short here, I really don't want to spend it tearing the front open if I don't have to.

I also replaced the carb-to-cylinder rubber hoses and checked all the exhaust junctions. No leaks there so far as I could detect.

 

[20774]

Be sure and inspect the filter at your next oil change...you might want to do it sooner rather than later. Take the filter out and pry off the metal ends...don't cut as that will just create small debris. Then unfold the filter and carefully look in each pleat for anything that looks unusual. If the chain is indeed whacking on the side of the case, small bits of aluminum would be seen in the filter along with possibly bits of the rubber that the chain runs across.

I'll have to go back and relisten, but I'm still not sure I hear anything that makes me concerned.

 

[marknreimer]

Be sure and inspect the filter at your next oil change...you might want to do it sooner rather than later. Take the filter out and pry off the metal ends...don't cut as that will just create small debris. Then unfold the filter and carefully look in each pleat for anything that looks unusual. If the chain is indeed whacking on the side of the case, small bits of aluminum would be seen in the filter along with possibly bits of the rubber that the chain runs across.

I'll have to go back and relisten, but I'm still not sure I hear anything that makes me concerned.

Thanks for the tip, I'll definitely do that. I'm due for an oil change next week anyway.

When you listen, focus on 41-43 second mark in the video. As the engine returns to idle there is a flutter. It's louder in real life. Comes and goes. Happens more when the engine is heated up I think.

 

[20774]

OK, now I hear that in the 41 second area. Can't say as I've ever heard anything like that. I've also never heard a timing chain slapping the case either. I think the timing chain would like slap the side if you were gassing it up and then backing off the throttle, creating some slack in the chain...that's kind of what you were doing.