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Old 09-18-2014, 12:38 PM   #1
kaspilo OP
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BMW - Twin parallel - cam chain rattles

I didn't realiaze how common this problem is among the f650gs, f700gs & f800gs owners until I started to read and research this issue.

When reaching to our dealers for a resolution most of them blow it off by saying "there is nothing to worry about"... "it is normal" ... "this is typical for this model"... but, I now better, IT IS NOT. This problem is related to the hydraulic tensioner, it does not hold hydraulic pressure, when the bike is at rest it leaks, it loses oil and air bubbles replace the volume of oil that leaked. The longer the bike is at rest the louder the cam chain rattles...

I have purchased a brand new tensioner, filled it (primed it) completely with fresh oil until no longer got any air bubbles and the piston was hard, replaced it on the bike, and had no rattle. Next morning I got the rattle again.. one morning I removed the tensioner without running the bike to find out that it had no oil.... BINGO! To confirm, I filled it out again with oil and laid it to rest over night on a paper towel.. surprise, within a couple of hours the towel was wet and the tensioner had no oil!

This is a relatively easy fix. BMW has to manufacture a hydraulic tensioner that does not leak and replace all those that failed. I suggest somehow we unite and put pressure on BMW. I'm open to suggestions.
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Old 09-18-2014, 01:36 PM   #2
bbenn75820
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yes they rattle for a few seconds, what damage does it do?
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Old 09-18-2014, 02:30 PM   #3
kaspilo OP
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If the rattle is loud that means the chain is really lose. It could eventually jump teeth and get out of timing or snap. Besides that, it is annoying and embarrassing to have such a classy bike with a tin rattle, to me we paid top $$$ and should be fixed!
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Old 09-19-2014, 09:02 AM   #4
kaspilo OP
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I think I was WRONG!!! I took the assembly out today and examined it closely. When the bike is at rest, then there is no hydraulic loading, the mechanical spring takes over to provide tension. As the chain gets slappier (longer), then the spring becomes too short and thereby there is no chain tension at start-ups until hydraulic pressure takes over. Resolution: Made and installed a shim/spacer between the spring and the nut (to push the tensioner forward)... let's see what happens, I will keep you posted.
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Old 09-19-2014, 01:51 PM   #5
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I don't read all the posts, are there reports of chains jumping?
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Old 09-19-2014, 09:05 PM   #6
ebrabaek
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I would like to offer the following advice. If you shim the acct it will not just put more pressure on the chain at startup, but throughout the entire running scheme. That is exactly what will accelerate your cam chain wear.
on other bikes a mcct ( m for manual) will let you adjust it so there are just enough pressure to keep the cc in line.
bmw actually did well with their acct...as if they put on a stiffer spring, it would be quieter....but accelerate the wear.
with a weaker spring it now does not accellerate wear....and oil pressure sorta acts like a hydraulic accumulator to absorb the pulses. If you exert more pressure by shimming.... I am certain you will accelerate wear. It will be quiet at start though.
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ebrabaek screwed with this post 09-20-2014 at 04:12 AM
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Old 09-19-2014, 09:29 PM   #7
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Originally Posted by ebrabaek View Post
I would like to offermthe following advice. If you shim the acct it will not just put more pressure on the chain at startup, but throughout the entire running scheeme. That is exactly what will accelerate your cam chain wear.
on other bikes a mcct ( m for manual) will let you adjust it so there are just enough pressure to keep the cc in line.
bmw actually did well with their acct...as if they put on a stiffer spring, it would be quieter....but accelerate the wear.
with a weaker spring it now does not accellerate wear....and oil pressure sorta acts like a hydrauluc accumulater to absorb the pulses. If you excert more presure by shimming.... I am certain you will accelerate wear. It will be quiet at start though.
Spot on, Erling. Harley-Davidson found this out the hard way on the Twin Cam motors. They were initially equipped with spring loaded cam chain tensioner. As you pointed out, a spring can only do what springs do, exert pressure all the time. This accelerated the wear on the shoes that bore on the cam chains. Caused a number of motor failures when chunks of the shoes got circulated in the oil. The engineers went back to the drawing board, and now they use hydraulic pistons to tension the cam chains. Just enough tension, and no more. A much better mousetrap!

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Old 09-20-2014, 04:14 AM   #8
ebrabaek
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Originally Posted by AK650 View Post
Spot on, Erling. Harley-Davidson found this out the hard way on the Twin Cam motors. They were initially equipped with spring loaded cam chain tensioner. As you pointed out, a spring can only do what springs do, exert pressure all the time. This accelerated the wear on the shoes that bore on the cam chains. Caused a number of motor failures when chunks of the shoes got circulated in the oil. The engineers went back to the drawing board, and now they use hydraulic pistons to tension the cam chains. Just enough tension, and no more. A much better mousetrap!

Jeff
Yeppers Jeff....
It is a rather large number of bikes that offer the MCCT as aftermarket option. Every time I thought the 8GS was noisy, I started my Suzuki DRZ...... Ha ha....And that was with a MCCT. I think they did good on the 8GS.
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Old 09-20-2014, 06:16 PM   #9
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Originally Posted by ebrabaek View Post
Yeppers Jeff....
It is a rather large number of bikes that offer the MCCT as aftermarket option. Every time I thought the 8GS was noisy, I started my Suzuki DRZ...... Ha ha....And that was with a MCCT. I think they did good on the 8GS.
You just can't stay away can you? Shouldn't you be busy making CF parts for the pride of Munich?
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Old 09-20-2014, 06:20 PM   #10
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You just can't stay away can you? Shouldn't you be busy making CF parts for the pride of Munich?
He he...... In the middle of selling our house, and buying another in Colorado...... But, There will be Carbon. You like the 12 by now...??? Enjoyed your ehhhh..... river cross..... uhmmm.... pushing
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Old 09-21-2014, 04:46 AM   #11
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Moving to the San Juans and switching to one of those? Sigh! May your jugs get stuck in a thick grove of Aspen trees.

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Old 09-21-2014, 06:01 AM   #12
ebrabaek
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Moving to the San Juans and switching to one of those? Sigh! May your jugs get stuck in a thick grove of Aspen trees.

Fred
Or as we say in Denmark... " May your a$$ itch, and arms be too short" 2 hrs north of the Juan's.
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Old 09-24-2014, 06:44 PM   #13
kaspilo OP
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UPDATE

I can tell you know that there is a noticiable difference after installing the spacer. The cold start is much quieter, not perfect, but quieter. As the bike warms up, the start up gets a little bit noisier, but not bad. This tells me that the cam chain is worn, that the reach of the spacer + the spring is not enough to compensate for the slack (thermal expansion) of the cam chain at higher temperatures.

This is a linear spring. By installing a 1.0mm thick spacer only pushed the spring and thereby the tensioner closer to the shoe, making the shoe put a little bit more tension on the chain.

I will try this assembly for a little while and provide you folks a periodic feedback. I will order a new cam chain just in case i need to replace it.

If you have tried any other solution to this problem and want to share it, please feel free to do so.
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Old 10-01-2014, 01:30 PM   #14
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Quote:
Originally Posted by ebrabaek View Post
I would like to offer the following advice. If you shim the acct it will not just put more pressure on the chain at startup, but throughout the entire running scheme. That is exactly what will accelerate your cam chain wear.
on other bikes a mcct ( m for manual) will let you adjust it so there are just enough pressure to keep the cc in line.
bmw actually did well with their acct...as if they put on a stiffer spring, it would be quieter....but accelerate the wear.
with a weaker spring it now does not accellerate wear....and oil pressure sorta acts like a hydraulic accumulator to absorb the pulses. If you exert more pressure by shimming.... I am certain you will accelerate wear. It will be quiet at start though.
This x1000

Quote:
Originally Posted by kaspilo View Post
UPDATE

I can tell you know that there is a noticiable difference after installing the spacer. The cold start is much quieter, not perfect, but quieter. As the bike warms up, the start up gets a little bit noisier, but not bad. This tells me that the cam chain is worn, that the reach of the spacer + the spring is not enough to compensate for the slack (thermal expansion) of the cam chain at higher temperatures.

This is a linear spring. By installing a 1.0mm thick spacer only pushed the spring and thereby the tensioner closer to the shoe, making the shoe put a little bit more tension on the chain.

I will try this assembly for a little while and provide you folks a periodic feedback. I will order a new cam chain just in case i need to replace it.

If you have tried any other solution to this problem and want to share it, please feel free to do so.
How many GS engines have skipped a tooth and cylinder hit the valves?... not many. and I don't recall anyone here with this issue... don't fix something that isn't broken.

These engines are noisy and you should live with it... What oil grade are you running? a too thin or too thick of an oil we make everything a little louder on idle.

This reminds me of my old 1998 VW GTI, people used to change the hydraulic tensioner for a manual one but they were never installed correctly or tight enough and caused more issues than the OEM hydraulic one lol
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Old 10-01-2014, 04:44 PM   #15
STED9r
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Edit-Disregard, went an read from the first page, has spring...... But now, spring rate comes into play an that's a whole other subject.

So, pressure is determined by surface area pressing against a moveable piston. Keep in mind this is a non compressible liquid, unlike a gas/vapor.
So, regardless of DISTANCE OF PISTON TRAVELING, the pressure is a constant and relies solely upon supplied hydraulic pressure.

Now, I've never looked at a bmw cam tensioner and without reading back some on this thread, haven't a damn clue whether or not it is also under spring tension. With that said, the pressure exerted upon the piston, of no spring present, remains the same once hydraulic pressure is achieved, via the pump, and will remain so whether at zero tolerance or full travel of the piston/plunger.

Now, go back to surface area. And again I haven't yarded one apart so haven't a clue of the inner workings and I'm addressing this issue in this paragraph under assumptions of no spring.
If the tensioner is pressed against the shoe, and the plunger/ piston is bottomed out against the "ceiling" of the cylinder, the surface area to move that piston now rests solely upon the size of the hole that hydraulic pressure is supplied and may not move that piston off that seat. Some of you whizbangs are smarter than me can can quote algebra crud so have at it, I'm just more concerned about tossing shims and the what not into things that may fix a short term issue while creating a larger problem tomorrow.

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