Soft Knock, 08 RT

[leadfoot]

08RT, 46K

I have not posted in a bit, but feel compelled to ask for a little help. I am quite mechanically inclined, as I pull all my services myself, but I have run up against a wall.

Last march I took a trip to daytona and got caught in some heavy traffic. Bike got warm, but not to an extreme. With the clutch pulled and in 1st gear I revved and heard a soft knock from the left side. I was worried I had gotten it too hot and desperately found a clear lane to get some air moving. Bike was sluggish. When I arrived at my destination the noise continued. I rode to the BMW dealership in Daytona and got the tech to come hear it. Wouldnt you know, no noise. I told him let it idle for a bit and it will start. He told me just dont get caught in traffic and dismissed it. Hmmm!

I bought a set of plugs thinking I may have fouled a plug or closed the gap, and the bike was running oddly on that cylinder, causing the knock. Old plugs looked OK, but I replaced them anyway. Bike ran great, no knock, I was very happy.

A month ago, the soft knock reared its head again. This time I started paying attention to when it was was doing this. The noise seemed most prominent with the bike in gear and clutch pulled. With it in neutral and clutch pulled, the noise was there, but less sound. And with it in neutral and no clutch, it quiets down. So for some reasonI dismissed it as non-combustion related. Prior, I had added a little fuel additive thinking I might have had an injection issue. Noise seemed to go away.

Now its back, and I am worried. It is not normal. Oil has been freshly changed prior. Two changes since the first issue. TB's are in sync. GS911 shows no faults. Valve lash is good. Bike is smooth as silk when cold, but if it gets above my normal operating temp seems to exibit this problem. Seems to be a bit sluggish when it starts with the knock issue. I know this is supposed to be a bullet-proof motor (to a point), but I am not familiar with the internals, and really dont want to be until I have no option.

My only guess at this point is a sticking injector causing it or carbon knock. It is rotational with the cycle of the crank, or so it seems. Noise has not increased in intensity since its start in Daytona. What about a bad coil pack? Could the coil pack be affected by heat?

Any input with this would be greatly appreciated. Until then I'm riding it and still listening for something I can pin point. Hopefully I've given enough info. Any questions please ask. All input is appreciated.

Thanks,
Jim

 

[azgman]

It is pretty hard to diagnose via the internet, but, could it be the cam chain tensioner?

 

[bmw_ken]

The description of the noise sounds like the transmission gear rattle that is common in the oilheads with hot tranny oil. I have heard of this also in the hexheads/camheads.

If gear rattle is the noise, I don't believe it is anything to worry about.

I am sure the experts will chime in.

 

[gstom]

Sounds like it could be a wrapped clutch plate if the sound is present when the clutch is pulled and in gear. I had a similar noise in my R1100RT-P and that was the diagnosis.

 

[leadfoot]

Sounds like it could be a wrapped clutch plate if the sound is present when the clutch is pulled and in gear. I had a similar noise in my R1100RT-P and that was the diagnosis.

GSTom, do you mean warped? If so, good point, I had not taken the clutch plate into consideration. Makes sense, only bad part is I will have to tear it down to see. Come to think of it, even with a fresh tune, the bike seems to have unusually increased vibration lately. Any of you folks have a good running test for this fault other than feel or a gut feeling?

If I get a significant agreement with your diagnosis I may just go into it. Think I will make the two hour ride to the nearest dealer for the tech to concurr first if I am 50/50 on the fault. He is a pretty good wrench as far as I am concerned.

Thanks Tom,

Jim

 

[PGlaves]

Get a decent mechanics stethescope and locate the noise.

Or use a long screw driver - handle at your ear, tip various spots on the case.

 

[leadfoot]

Get a decent mechanics stethescope and locate the noise.

Or use a longs screw driver - handle at your year, tip various spots on the case.

Will do Paul. Great advice, as usual! Start with the simple methods....

Will report results.

 

[deilenberger]

I'll just add - Harbor Freight has a wonderful mechanics stethoscope.. usually $3.99, often goes on sale for $1.99 (problem is getting out of HF without spending an additional $98..)

One of the best tools in my toolbox, it allows me to track down the noise I'm obsessing over at the moment.

 

[gstom]

GSTom, do you mean warped?

Yes, warped. That's what happens when posting BEFORE my morning coffee.

BTW I have not repaired the clutch as it works OK except for the noise. I mainly hear it when I am stopped at a red light after the bike is warmed up. Your history of the noise appearing after a slow cruise in the Daytona parade of bikes makes me think you could have overheated the clutch plate then and warped it.

And your description of the noise as a "soft knock" is how I would exactly describe my noise. The diagnosis of the noise I got was from the mechanics at Bentonville BMW, one of whom was familiar with the common clutch problems associated with "Cop" bikes.

 

[PGlaves]

I would have a concern if I thought I had a warped clutch assembly. It seems to me that in going around and making noise it would be putting some abnormal stresses on the transmission input shaft. The end results would likely be sharply increased wear on the input shaft splines and possibly damage to the input shaft front bearing.

I had personal experience of such when the clutch housing (flywheel) was warped and would think warping of any of the assembled clutch pieces could cause the same problems.

 

[leadfoot]

Update: Got home yesterday and the noise was there. I took my longest screwdriver and listened to what I could, but it was rather difficult on the RT with the tupperware on. Tonight I will expose the engine and give a better listen. The sound is there in all 3 situations , in gear clutch pulled in, neutral clutch pulled in, and neutral clutch out. Sound is louder to lighter with respect to the 3 situations. I have to lightly rev it to hear the knock, it is not there at idle. Loading and unloading the engine produces the knock (which really bothers me), but to best describe it, it is a "soft" knock. I am going to bring a borescope home from work today and look at the piston top for that dreaded imprint, then maybe at some internals with the rocker covers off. It's not bad enough to keep me from riding it, but it is there.

Thanks for the HF tip Don. Yeh, that $3.99 stethoscope will likely cost me a hunderd dollars!

 

[leadfoot]

Got the tupperware off this evening. As before, the engine is quite sound when cold. After a good warming up the noise began. I went all around the bike checking for noise with a long phillips. The knock is definitely in sync with the rotating assembly. Seems more prominent near the Txmsn housing. It also is definitely more clear with the clutch in and in gear. Still have not understood why.

I have tried to look at as many clutch diagrams as I could, and cannot get my mind wrapped around the noise with regards to it coming from that area. I would like someone to give me a good explanation of the compensator and its operation if they could. Definitely sounds like something is loose back there.

Still in the diagnostic stages, so I am not tearing it down until I am reasonably sure or have someone more experienced with this engine diagnose the noise.

On a side note, last oil change (500 miles ago) I used a fine mesh filter during the hot draining process. No debris whatsoever.

So on it goes......

Jim

 

[leadfoot]

I putting it back together for now. I have to give a couple MSF Courses the next two weekends and the second course is going to take me near a Dealer. Hopefully my schedule will get me by there for a second opinion. Until then i am open to any and all opinions on the issue.

Thanks,

Jim

 

[leadfoot]

Made it to Harbor Freight today and picked up a stethoscope for $3.99 that ended up costing me $116.00. Honest, I really needed it!!....Anyway, I got a buddy to operate the throttle while I probed around (that thing works pretty good). In my opinion, and my friend's, the noise is coming from the clutch area. It does transition forward to the front of the engine, but is not as prominent. I can alter it by pulling the clutch. It does not go away, just changes in intensity. Sounds like something is softly knocking in rythm to the rotating assembly.

On another note, I have been scouring the net for a documented sequence for a clutch replacement, and have just found bits and pieces. I did however find a post almost identical to my problem. Don had quite a few opinions on it. While my bike is not in warranty anymore, I do not mind doing the work, I just want to be as sure as I can before I begin. Link to the similar post is below.

http://bmwsporttouring.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=296604&page=1

Next move, unless something positive shows up, will be an opinion from the nearest BMW tech. I will have to take it from there.


Jim

 

[leadfoot]

New angle?

Got home today and immediately used the stethoscope to listen to the engine while it was hot. Starting to feel the noise is from the engine, really hard to pinpoint. Sat and ran the engine to a pretty hot point, noise got worse. i swear it sounded like low oil pressure, rods rattling.

I decided to to another hot drain to check for debris. Got the pan, filter, tools. Took the plug out approximately 5 minutes after shut down. I knew the oil would be hot and thin, but when I removed the plug the oil sprayed out like it was coming out of a high pressure waterhose until almost empty. Very high pressure! Never seen this.

My immediate thought was the pressure in the crank case was so high that it was affecting the oil pressure/flow at high RPM. I am looking at the ventilation system now to make sure I do not have an obstruction. Large vent tube on left side has a kink that cuts flow in half,, not sure if it is collapsing when operating. Need to refill and observe.

Sure would like a little help on this. Called Bmw shop but tech must not have gotten the message to call me back.

Ideas? Thoughts?

 

[PGlaves]

The bad news: it shouldn't have crankcase pressure.

The good news: it seems to have good rings.

I'm not sure what to advise except check the ventilation.

And if reasonable, run it again and then remove the oil filler cap to see if you can tell whether it has pressure again.

 

[DROOT153718]

I would run the engine hot. Take off the e filler cap and put my hand over the hole for about 10 seconds. Let go and see what appens.

I would be screwing an oil pressure gauge in checking hot and cold.

David

 

[leadfoot]

The bad news: it shouldn't have crankcase pressure.

The good news: it seems to have good rings.

I'm not sure what to advise except check the ventilation.

And if reasonable, run it again and then remove the oil filler cap to see if you can tell whether it has pressure again.

Ran it again. shut it off twice and removed the fill cap. no pressure. May have fixed this issue by rotating the hose 90 degrees. Sadly though the noise still exists.

Oddly, the most prominent location of the knock is at the aft end of the starter, very strong. Maybe resonating to the starter but real odd. Is the starter drive on this engine a constant engaged unit?

Still, the noise is only after a good heat-soaking of the engine-tranny. Cool off for 10 minutes it goes away.

 

[leadfoot]

I have scoured the GS forum for clutch failures and possible sources. These GS guys seem to see harder riding so I thought failures or faults would be more evident. Saw some transmission and clutch spline nightmares, but still cannot put my finger on this.

Only thing I cannot find info on is the compensator weight. I would like to know if noises can be expected from this weight and if failures are common. I cannot find out if it is an articulating weight or a fixed one. An education would be appreciated.


By the way, thanks for the input Paul!

 

[DROOT153718]

At 138 thousand miles, I had a noise like that. It seemed most prominant on HOT days. Engine cold it was not there.

In the end, my clutch was about to strip. I pulled the starter, turned the rear wheel with it in gear. I could see the shaft turning in the clutch hub. I then measured the amount the disc turned with shaft still. It was 5/8 inch ready to strip. I replaced the disc and the noise went away for a while.

Noise was the loudest in third gear about 3,000 rpm under light load.

The crank moved up and down .004 inch.

David