K75 Engine noise

[bgcameron]

I spose you didn't find any stray sparks from the leads behind the plug cover or coil cover in the dark?

No sir, not yet anyways. Once I have the alternator back in with new bushings then I will report back to you.

[bgcameron]

Thought I would pull the front cover off today and inspect the timing chain. Here is a video of the movement in the tensioner.

[Laitch]

Chain tension is created by oil pressure acting on that pedestal pushing upward on the lower run of the chain. You might check behind the block beneath the pedestal to determine if the oil passage is clogged. BMW offers little guidance on when to replace a timing chain. If the tensioner doesn't look worn and the oil passage is clear, you could always replace the chain. Sometimes they last over 100K miles or more; sometimes they stretch sooner. I probably wouldn't have been bothered by the noise I heard in your first video.

That's all I've got. Maybe somebody else will chime in.

[The Mighty Gryphon]

I think the tensioner mechanism doesn't look like it's working properly.  As Laitch mentioned, oil pressure extends the pintle, but there is a ratchet inside that prevents the pintle from backing down the way yours is. I would take the tensioner off the engine and, as Laitch mentioned, check the oil passage and ratchet.

[daveson]

That's absabloodylutely spotless.

[The Mighty Gryphon]

BMW offers little guidance on when to replace a timing chain. If the tensioner doesn't look worn and the oil passage is clear, you could always replace the chain. Sometimes they last over 100K miles or more; sometimes they stretch sooner.

I replaced the chain on one of my bikes at 108,000 miles.  These chains aren't long enough to show a lot of stretch that can easily be measured, the wear evidences as "side curve".  I checked it by stretching the chain out and and then bending it into an sweeping curve on a flat surface.  It's been a while, but I think a new chain has a depth of about 1/2-3/4" to the curve.  The old chain I replaced was close to 2".  The side bend play could possibly allow the chain to slap around and hit the case, especially if the tensioner isn't working properly.

If the tensioner has been allowing the chain to slap around for a long time I wouldn't be surprised if the chain is worn.  It's one of those situations where the wear accelerates more wear.

As far as the case slapping, have you seen any metal in the old oil?  Since the cases are aluminum it won't be magnetic. 

[Laitch]

Inspect the rearward surface of the hole into which the crankshaft seal is mounted on the engine side the timing case cover. Gouges or chipping in that surface indicate chain slap.

[bgcameron]

Everything looks clean around the crankshaft seal. The slight play in the tensioner seems to be caused by the ratchet being in between two point of engagement.

[Laitch]

Time to move on, bg.  You're doomed to riding it.

[The Mighty Gryphon]

Can you get the ratchet to engage by GENTLY pushing up on the tensioner pintle?  Have you checked the orifice that supplies the oil pressure to the tensioner?  I think there is an o-ring that surrounds that orifice, is it there?

[bgcameron]

Tried but it wouldn't click up any further. I showed the video to the local expert at the bmw dealer and he said its normal. You're right Leitch, I am doomed to ride it! I will update you guys if I make any progress.

[bgcameron]

Putting it all back together and I noticed some scale in the water pump area. White crusty residue on the impeller, black flaky stuff in the outlet pipe. Any recommendations for a coolant flush product?

[The Mighty Gryphon]

I've used Prestone cooling system flush with distilled water for the block, and white vinegar to clean out the radiator inside and out after it's been removed from the bike. 

The Prestone stuff does a good job on the whole system, but you might have to run two flushes if the scale is really bad.  The vinegar does a good job of cleaning out the inside of the radiator as well as softening up the bugs that are jammed into the fins so they can be flushed out with a good rinse.

[daveson]

Just double checking before the rocker cover goes back on, does the spring make good bare metal contact?

Are there any tell tale signs like black tracking marks where sparks might be jumping?

Now that you found a way to reproduce the sound while the bike is stationary, you might be able to use a screwdriver to pinpoint the source more closely.

[bgcameron]

Just double checking before the rocker cover goes back on, does the spring make good bare metal contact?

Are there any tell tale signs like black tracking marks where sparks might be jumping?

Now that you found a way to reproduce the sound while the bike is stationary, you might be able to use a screwdriver to pinpoint the source more closely.

Well she's all buttoned up now, but I did check the spring and its contact area and everything looked good. I am going to run it tomorrow and see what I can find out.

[bgcameron]

Took it out tonight.. No sparks seen from the plug wires. Given that it was night time and less traffic, I was able to spend more time leaning on either side of the bike to listen for the noise. I seems to be equally as loud from each side. Now I am wondering if it is something in the drivetrain...maybe the clutch? The clutch seems to make a bit of a clack noise when you are letting it out to get moving, so maybe it is related.

I am at the point now of taking it in to get it looked at. Normally I am more ambitious to fix these things myself.. but my dad passed away yesterday and I just want to take it easy for a while and not stress about my stress-relieving machine.

[daveson]

Arh shit bg I know that's a heavy blow.

I'd call this noise a non urgent problem. I recon you can just ride for a while and have another look sometime down the road.

[The Mighty Gryphon]

Sorry to hear about your dad. 

My advice on the bike is to just go and ride it.  My K75 has rattled at various rpm with an assortment of clanking noises since the day I got her.  45,000 miles later she still runs great and does 7-800 miles days at 85mph with aplomb.

You have checked it out and mechanically it looks okay.  Do a thorough service, then put some miles on it and enjoy it. 

[Laitch]

The clutch seems to make a bit of a clack noise when you are letting it out to get moving, so maybe it is related.

If the clutch clacks when the clutch hand lever is released, the clutch arm is likely to be hitting the muffler. If that is the case, the arm could also rattle against the muffler at certain vibrations. It is no cause for worry and a few millimeters of adjustment will stop the rattle.

[daveson]

 I think your saying it's easier to reproduce going uphill.

Next time you do a clutch lube, it would be a simple matter to check for output shaft endfloat, and look for balance marks for the clutch.

[The Mighty Gryphon]

It's the nature of the K75 muffler that it is very close to the clutch arm at the end of the clutch cable.

A simple test(do it after correctly adjusting the clutch) is to pull the clutch lever all the way in, and then let it snap out.  Do you hear a clank down by the muffler?  Do this a couple times.  If you hear it clank, take up a little bit of cable slack with the adjuster at the lever.  Only take up a tiny bit and check again for the clank.  It should only take a couple mm to stop it.

Outside of this minor adjustment, refer to my advice above.

[bgcameron]

I had a look at the clutch lever and thought that it's proximity to the muffler was the likely cause. I did the adjustment, which gave it much more clearance. Unfortunately it didn't fix the mystery noise.

[The Mighty Gryphon]

Okay, go get some good ear plugs(I like 3M Skull Skrews) and put some miles on it. 

[Laitch]

I am at the point now of taking it in to get it looked at.

I've listened to both your videos. I hear a slight rattle at 12:00 and 18:00. It seems to happen when you accelerate a little. It is so slight that its power to distract you is incomprehensible to me. It's as far from a clack as it is from a quack. All I can come up with is that you're riding at revs that are too low for the gear. Bricks will rattle a little when that happens.

As suggested, earplugs—and shifting at higher revs—are the remedies; the earplugs also preserve your hearing from being damaged by high frequency noise, too. I always wear this reusable, flanged style. Several companies manufacture them.

[The Mighty Gryphon]

Here is what is the most likely cause of your noise.  A sloppy fit for the balance shaft drive dog.  The location in the engine and the parts involved will cause the resulting sound to be transmitted throughout the entire engine making it sound like it's coming from everywhere.


DSCN1758.JPG (46.82 kB . 768x576 - viewed 733 times)

If you like you can tear down your engine to confirm it.  My bike has made an awful clank at low rpm and under heavy load when I don't downshift enough since I got it 6 years and 45,000 miles ago.  Despite the noise it has run like a bear and taken me across country 3 times since I got it. 

I've found that keeping the revs up and wearing earplugs has made our time together much less stressful.  It also helps a lot to keep your valve clearances as close to each other as possible as well as close balancing the throttle bodies.