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Old 02-27-2012, 06:25 AM   #151
Indy Unlimited
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Hey Chadams, did you safety wire the old chain to the new chain to feed it thru or did you connect it with a master and then disconnect it after feeding thru. A little more detail would be appreciated. Great work.
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Old 02-27-2012, 06:28 AM   #152
JRWooden
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Thanks chadams!
Very nice detective work, as well as wrenching!!!
That is a good point on the extra load from the water pump drive ... I had not considered that factor.

About how many miles do you have on your bike?
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Old 02-27-2012, 07:18 AM   #153
epicxcrider
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Quote:
Originally Posted by JRWooden View Post
Thanks chadams!
Very nice detective work, as well as wrenching!!!
That is a good point on the extra load from the water pump drive ... I had not considered that factor.

About how many miles do you have on your bike?
In most (all?) vehicles timing chains drive the water pump, correct? Don't know why the stretch / wear on this one is so high.
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Old 02-27-2012, 09:04 AM   #154
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Originally Posted by epicxcrider View Post
In most (all?) vehicles timing chains drive the water pump, correct? Don't know why the stretch / wear on this one is so high.
It's certainly not UN-common for them to be driven from the cam.

I don't know why we seem to have higher wear rates ....
Under-designed chain
Poor chain metallurgy
Poor tensioner design (there is a new heavier tensioner spring out - I have one on order)
don't know...........

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Old 02-27-2012, 10:02 AM   #155
MikeMike
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Hey JR, I was told here that the new spring design was not new per se but had been updated in 2008.
When you get the new assembly can you compare the spring to your old one and provide the build date for your bike?
Very cool that a couple of mysteries are being solved!
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Old 02-27-2012, 10:05 AM   #156
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Originally Posted by MikeMike View Post
Hey JR, I was told here that the new spring design was not new per se but had been updated in 2008.
When you get the new assembly can you compare the spring to your old one and provide the build date for your bike?
Very cool that a couple of mysteries are being solved!
MikeMike - I agree, I'm not sure how "new" this heavier spring design is exactly... but since it's only a few bucks I ordered one. When it arrives I'll compare it to what I have installed now and post back!
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Old 02-27-2012, 11:39 AM   #157
epicxcrider
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Originally Posted by JRWooden View Post
It's certainly not UN-common for them to be driven from the cam.

I don't know why we seem to have higher wear rates ....
Under-designed chain
Poor chain metallurgy
Poor tensioner design (there is a new heavier tensioner spring out - I have one on order)
don't know...........

I'm guessing some of it may be that on the motorcycle the noise and performance loss are much more noticeable than in a car or (especially) truck where the chain wears over time.
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Old 02-27-2012, 02:04 PM   #158
chadams
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Originally Posted by Indy Unlimited View Post
Hey Chadams, did you safety wire the old chain to the new chain to feed it thru or did you connect it with a master and then disconnect it after feeding thru. A little more detail would be appreciated. Great work.
I removed one pin from the new chain, then pushed one pin to the outer link of the old chain then used this old pin to link the two chains.
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Old 02-28-2012, 01:57 AM   #159
chadams
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Just finished and went for a test ride all is good. The motor has never been so quiet even when new.

Total time for the job was about 5 hours and the parts I change was the cam chain, tensioner spring, tensioner, top chain guide (as it was broken). All other parts I reused.
Tomorrow I'll ride it to work and back to see how it goes, approx 150km trip.

Update: Made it to work (75km) no leaks and the motor sounds sweat.....
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chadams screwed with this post 02-28-2012 at 05:48 PM
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Old 02-28-2012, 07:51 PM   #160
chadams
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Originally Posted by JRWooden View Post
Thanks chadams!
Very nice detective work, as well as wrenching!!!
That is a good point on the extra load from the water pump drive ... I had not considered that factor.

About how many miles do you have on your bike?
Just on 90,000km, but the chain was bad from 60,000km
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Old 02-28-2012, 09:18 PM   #161
JoelWisman
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Nice work all, sad I missed this thread till now.

A few notes that may be helpful.....

1: The timing chain is NOT oil tensioned. If you look at the tensioner, oil pressure is not applying any significant force to the chain. The timing chain is oil damped.

My theory about the chain failure is that the combination of a fairly radical cam profile combined with a super light flywheel combined with a longish cam chain is making the chain very susceptible to harmonic oscillations loading and unloading the chain multiple times per crank revolution.

This theory was put fourth when my engine became the first to need to be pulled apart for a stretched chain and cemented when I inspected subsequent stretched chains at other dealers.

A manual tensioner is not the way to address this IMO as they do much less to damp harmonic oscillation.

A possible source of air ingress to the pressurized oil is an internal part of the gasket on the clutch cover, so don't reuse it, torque it correctly, and check the factories torque on these bolts as BMW is notorious for leaving things loose.


2: The start-up death rattle is from oil drain back and subsequent filling in with air in the tensioner which bleeds rapidly. Not all oil filters stop bleed back as well as others and they do progressively poorer as the oil fills with more fine particulate. I do not believe this start up death rattle is material or important as long as you do not rev the engine while it is occurring.


3: A stretched chain is easy to hear as initially it won't happen when the engine is cold after the first few seconds. It will not be present at idle for the first 10 minutes or so but will then become apparent. If you are real concerned, start up your bike and let it idle till the cooling fan cycles on and off several times. If you start hearing a rattle towards the latter fan cycles, your cam chain is stretched. It is the only component that rattles only once the engine is hot hot but initially at no other time. The rattle is completely unmistakeable, anything short of a deaf guy will hear it and know it can't be right.


4: You measure chain stretch by taking the end off the chain tensioner and measuring how far you can force the puck in before it tensions the chain. I used to have measurements in my desk but they were lost when I was terminated without warning. Someone who has a new chain will have to measure this, then someone else who's chain is rattling when hot hot, then we will have measurements. To date, BMW does not specify any way to measure chain stretch.


5: I am glad it is someone else trying a master link as I wouldn't want to be the first :) There won't be any issue with clearance that I can think of, but the extra weight may or may not contribute to chain oscillation.


6: I don't know how much it matters, but many ham fisted BMW techs break the top chain guide towards the exhaust while removing the cam cover for seal replacement or valve adjustment. The wire harness is totally in the way when removing the cover and the exhaust side top guide takes a hit if the tech or owner isn't careful.

I took loads of grief from techs and the service manager when I wouldn't let techs pull the broken piece out and ship the job since what the customer doesn't know won't hurt him.....

Eventually my old shop started stocking that piece as it was always in Germany and customers weren't happy when we pulled the cover to do an adjustment, then had to keep the bike for a few weeks waiting for the part.

I am friendly with many other shops and have heard them comment on this part being broken as well. Some replace it, some pretend nothing ever happened cause they like my service manager figured it wasn't important.

I don't know how important this part is, but I have to believe BME put it there for a reason and it is even possible it is leading to some of the early cam chain failures.

I have since had the cam cover off on 2 F8's I helped friends service, and both had old discolored broken exhaust side top chain guides.

This may or may not be an issue but it is sure something to watch out for.

7: If a manual tensioner blocks the oil flow through the tensioner cavity, you will loose the cam in a hurry.

8: I think the cam could twist the water pump shaft in half without stretching the cam chain at all. I don't think the water pump is related to any of the F8's cam chain woes.

Just my thoughts but helpful perhaps?
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Old 02-29-2012, 04:43 AM   #162
epicxcrider
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Thanks for the notes!
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Old 02-29-2012, 07:53 AM   #163
JRWooden
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As always - Thanks Joel!

Not having had mine appart yet, I had "assumed" the oil-based tensioner dealie also tensioned, not just damped.
I have one of the newer stronger tension springs on order (not sure if my bike has the old or new, but for $5 I'll be a sport).

With it's less radical cam profile, I would "assume" that the F658GS would be less likely to experience this problem... or it would not occur until a higher mileage.

I'm guessing the top chain guide you are talking about is: 11317689494 cleverly named "sliding piece" ...
For $4 I'm putting one on my list of crap to have on hand ... my 24K mile valve check is coming up...

Just printed out the page in the manual for re-torquing the clutch cover ... I'll do that this wkend!
As a small community service here's the details:


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Old 02-29-2012, 05:11 PM   #164
Dieselboy OP
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Quote:
Originally Posted by chadams View Post
Just finished and went for a test ride all is good. The motor has never been so quiet even when new.

Total time for the job was about 5 hours and the parts I change was the cam chain, tensioner spring, tensioner, top chain guide (as it was broken). All other parts I reused.
Tomorrow I'll ride it to work and back to see how it goes, approx 150km trip.

Update: Made it to work (75km) no leaks and the motor sounds sweat.....
Dieselboy= 40 hours and massive project
Chadams= 5 hours and didn't even clean the dirt off the engine

Hmmm. Which to choose......

Chadams, I had the same experience with the engine being quieter than when new.

Quote:
Originally Posted by JoelWisman View Post
Nice work all, sad I missed this thread till now.

A few notes that may be helpful.....

1: The timing chain is NOT oil tensioned. If you look at the tensioner, oil pressure is not applying any significant force to the chain. The timing chain is oil damped.

...
Joel, thanks for chiming in. Your #1 comment really has my attention. So the tensioner failing isn't causing the cam chain to stretch through lack of tension but rather through contributing to increased oscillation when air is allowed in? Or am I missing the mark?

My stated plan is to replace the tensioner @ 25000 miles. Good plan or not?
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Old 02-29-2012, 06:16 PM   #165
JoelWisman
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Quote:
Originally Posted by Dieselboy View Post



Joel, thanks for chiming in. Your #1 comment really has my attention. So the tensioner failing isn't causing the cam chain to stretch through lack of tension but rather through contributing to increased oscillation when air is allowed in? Or am I missing the mark?

My stated plan is to replace the tensioner @ 25000 miles. Good plan or not?
You have it right, though air ingress is just one issue, and the part about the air coming from a leak on the internal clutch cover gasket is my personal theory.

The theory has some substance to it though, and went all the way up to Shawn, the USA technical boss who called me to talk about it, then issued a PuMA action, which sadly I can't reprint do to signing a "non-disclosure" on it.

Yes I'm tooting my own horn :) but not many shop foreman get to talk at length with the technical boss in charge of all FSE's

The tensioner running on aerated oil will work just like a shock thats aerated, not worth a damn, but the tensioner can also wear out and loose damping, or as a birdy tweeted, some might have come from the factory with way too much clearance and not damp worth a damn.


This I know for certain. That timing chain LOVES to oscillate. The light flywheel is the main cause.

This I believe but don't know to a certainty: Tension is not the answer, proper damping is.

Amongst other things when working the cam chain issue, I took high speed video of the exhaust side of the chain with the cam cover removed and got a face full of oil doing it.

Using a screw to tension (no spring or damper) regardless of how much tension I applied, massive oscillation would occur with tension simply changing at what RPM it occurred.

Same with a bad damper, but with a good one, the chain ran "relatively" smooth.

I wish I still had the video. even at 120 frames a second the chain would turn into a blur at that sweet RPM, and the range of it's movement was terrifying.

Good damper and it moved more then I personally liked, but was an order of magnitude better.

Yes, If I still owned an F8 I would change the damper regularly, perhaps half way between stator changes lol :)
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