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Old 02-22-2013, 10:03 AM   #46
JoelWisman
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I figured that when the noise was cam chain it was being caught every time as well but I just ran across a guy who took his bike into a big USA dealer that missed the noise last week so in at least some places it's still being missed :(

Heres when the noise first begins happening: At the beginning the noise will appear after the second or third time in a row when the cooling fan cycles on. The cam chain is the longest part of the engine as it goes from the bottom of the engine to the top and then back. It is therefore the item that expands the most as it gets hot and so first gets slack when it gets hottest and the timing chain tensioner runs out of adjustment range. The timing chain is the last thing to get hot hot as it isnt directly connected to the engine anywhere and does not actually bathe in oil the F8 being a dry sump design. As the chain stretches further the rattle will begin the first time the cooling fan comes on and eventually at all times while the engine is on shortly before it fails.

Heres why it fails: The K7X engine having a super lightweight flywheel design, the crankshaft accelerates and decelerates considerably between each combustion stroke. This and the cam shafts aggressive profile results in the timing chain loading and then becoming slack twitch per crank shaft revolution. This repeated slackening and then tension results in the rapid stretching of the timing chain with the currently spece'd units. It doesn't make the noise at higher RPMs as the crank does have enough rotating inertia to keep the chain under tension for the brief intervals between combustion cycles at these higher speeds, so, initially you hear it when the cooling fan is on LOWERING THE ENGINE RPM.

Heres how you check: First remove the timing chain tensioner so that the tensioner will not deploy further as removed, then remove the tensioner. Once removed, pull on the tensioner. If the tensioner is on its last notch of adjustment (or within 2 notches) the cam chain has stretched excessively.


FYI. The first time I heard the noise a stretched timing chain makes I thought it was something in the clutch or possibly the HLM or big end bearings but the noise changes somewhat as the chain becomes more stretched.
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Old 02-22-2013, 02:49 PM   #47
JRWooden
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Quote:
Originally Posted by JoelWisman View Post
...
Heres how you check: First remove the timing chain tensioner so that the tensioner will not deploy further as removed, then remove the tensioner. Once removed, pull on the tensioner. If the tensioner is on its last notch of adjustment (or within 2 notches) the cam chain has stretched excessively.
...
Ok, you just came back for a visit
So I want to be a good host and all ...
Here's a beer and a steak ...
Beer cold? Good!
Can I get you another?
Steak the way you like it?
Ahhhhhhhhh great!

Now ...
Notches?
What stinking notches?
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Old 02-23-2013, 02:01 PM   #48
Steveman OP
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Thx Joel,

will check the noise once I got the bike back on the road. Currently we have 15 inches of fresh snow
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Old 02-25-2013, 01:40 PM   #49
JoelWisman
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Originally Posted by JRWooden View Post
Ok, you just came back for a visit
So I want to be a good host and all ...
Here's a beer and a steak ...
Beer cold? Good!
Can I get you another?
Steak the way you like it?
Ahhhhhhhhh great!

Now ...
Notches?
What stinking notches?
Sorry, the tool to check timing chain stretch has notches. You screw it in where the factory tensioner goes, turn the engine in the normal direction of rotation with the back wheel, remove the spring from the tool, then remove the tool and the notch your on tells you how stretched the chain is. It is basically a normal style tensioner cum tool wish is the sort of tensioner everyone but BMW uses lol. I guess I only half finished the above post due to late hours and only being half awake.

You can also measure the fully extended position of factory tensioner, pull the tensioner and see how close you can get to that by pushing a rod in under firm hand pressure. If you get within 1/8" then when the bike is hot the chain is becoming un-tentioned

I had hoped BMW would have fixed this issue by now but am hearing from my friends on the inside that the issue is far more common then desired. It's a big pain in the but to change the timing chain but it beats letting it break which destroys the engine :(
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Old 02-25-2013, 06:52 PM   #50
JRWooden
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Thanks Joel!
Now it's clear!

I'll ask to see their tool next time I'm at the local dealer and see if they have one........ or at least if they know WTF I'm talking about!
I would like to see what it looks like ........


Seems like BMW needs to create a cam chain replacement kit with a master link ... like one of our own did here, so that an engine tear-down isn't required ...

In case anybody missed it here's the link:

http://www.advrider.com/forums/showt...6#post18082546
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Old 02-25-2013, 07:00 PM   #51
JoelWisman
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I hate to say it, but knowing that if the cam chain breaks valves hit pistons and usually the end result is a completely destroyed engine, I wouldn't feel comfortable with a master link chain.

I'm happy to use a master link chain for a drive chain, but as a cam chain.... Not me personally.

In my experience as often as not master link chains fail right at the master link and unless your buying a chain engineered for this engine, you aren't going to know how we'll it holds up until the day it breaks.

I salute the inmates bravery, but will not be copying them until a few hundred others do this AND have it not fail in 80,000 miles.
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Old 02-25-2013, 08:07 PM   #52
JRWooden
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Originally Posted by JoelWisman View Post
I hate to say it, but knowing that if the cam chain breaks valves hit pistons and usually the end result is a completely destroyed engine, I wouldn't feel comfortable with a master link chain.

I'm happy to use a master link chain for a drive chain, but as a cam chain.... Not me personally.

In my experience as often as not master link chains fail right at the master link and unless your buying a chain engineered for this engine, you aren't going to know how we'll it holds up until the day it breaks.

I salute the inmates bravery, but will not be copying them until a few hundred others do this AND have it not fail in 80,000 miles.
It is not a clip-style master link, but I do, very much, see your point!
Esp. since a failure very likely means total engine destruction.
but damn the alternative is a lot of work...........
I'd almost rather add a master-link style chain replacement to every other valve check...

Is this an issue on any other BMWs like the K1200 series?
Chain length would be similar ?
and while it is 4-cyl. I would guess a light flywheel there as well?

I've had my share gotta get ready for work ...

Thanks Joel!
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Old 02-25-2013, 08:12 PM   #53
JoelWisman
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Not nearly as common, but yeah, the k1200 and 1300 bikes had occasional chain derailment problems but it was traced to faulty tensioners and guards. The K7X line, AKA twin cylinder Rotax are the inlet engines with chain stretch problems between 10,000 and 80,000 miles
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Old 02-26-2013, 06:43 AM   #54
JRWooden
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Originally Posted by JoelWisman View Post
Not nearly as common, but yeah, the k1200 and 1300 bikes had occasional chain derailment problems but it was traced to faulty tensioners and guards. The K7X line, AKA twin cylinder Rotax are the inlet engines with chain stretch problems between 10,000 and 80,000 miles
Thanks ....
... by the time the summer is over I hope to be 1/2 way to 80K

Any idea how much of the wear is on the guides vs. chain its self...???
If new guides inserted from the top of the engine during a valve lash check can significantly extend the interval before which the engine needs to completely disassembled for a new cam chain that's a good thing in my book...

I kinda forgot ... having the F658-twin my cams have less lift .... I would kinda think that would help?
Did you seen any evidence that would indicate less wear issues with the 658?

I looked it up: 7.2 mm lift vs. 9.64 mm

JRWooden screwed with this post 02-27-2013 at 03:22 PM
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Old 03-01-2013, 08:26 AM   #55
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PS: I asked one of the mechanics at the local dealer if they had the cam chain wear measuring tool and got a look that was between are you a can-short-of-a-six and wow that would be a cool tool to have ........

He asked me if I had a P/N for it... and he'd put one on order...
Anybody got the P/N?
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Old 03-02-2013, 07:57 PM   #56
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Question Oopsy

I just made a little mistake that has me keenly interested in this thread. I started my 800 up to let it warm up before heading home, then got distracted. It was running for about a half hour. I thought it would be fine, since I just spent a lot of time getting the cooling fan freed up a week before. Also it was maybe 55 Deg F at the time. But when I checked on her, she was totally overheated - temp gauge was maxed, warning lights, etc. I seem to remember hearing the rattling like Joel is describing. I shut the bike down right away, and could hear the coolant boiling.

I let her cool down, and made it home. I plan to leave her parked until I can change the oil, flush the radiator, and have another look at that damn cooling fan. Then I will start her up and listen closely to the engine. Is there anything else I should do? Unfortunately taking her to a dealer isn't an option right now. Is there any way to upgrade the cooling fan? Seems like it can't overcome the smallest speck of dust.
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Old 03-02-2013, 09:41 PM   #57
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Originally Posted by Mongo357 View Post
I just made a little mistake that has me keenly interested in this thread. I started my 800 up to let it warm up before heading home, then got distracted. It was running for about a half hour. I thought it would be fine, since I just spent a lot of time getting the cooling fan freed up a week before. Also it was maybe 55 Deg F at the time. But when I checked on her, she was totally overheated - temp gauge was maxed, warning lights, etc. I seem to remember hearing the rattling like Joel is describing. I shut the bike down right away, and could hear the coolant boiling.

I let her cool down, and made it home. I plan to leave her parked until I can change the oil, flush the radiator, and have another look at that damn cooling fan. Then I will start her up and listen closely to the engine. Is there anything else I should do? Unfortunately taking her to a dealer isn't an option right now. Is there any way to upgrade the cooling fan? Seems like it can't overcome the smallest speck of dust.
The following is what I would do. Glycol/water is just that. If it has no signs of a blown head gasket, thus contaminated with oil, then I would leave that alone. I would however change the oil, as it might have taken some hit sheered the polymers.... I say might. The oil would also have transported bad stuff away as a result of the overheating. It is a cheep way to buy insurance, along with the filter. The rattle at shut down, would lead me to check the valves as well. Just to be sure. If the motor sounded normal prior to shut down, I would forgo the valve check. Then start it up, but not before you spin the heck out of that fan with compressed air. As the engine was running when you shut it down, I see no need for a tear down. Even the valve check is just to be safe. They dont really move the tolerances at overheating, but it is a quick thing to check. That is the way I would proceed. Hopefully all will be well. Let us know how it goes.
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Old 03-03-2013, 02:58 AM   #58
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The following is what I would do. Glycol/water is just that. If it has no signs of a blown head gasket, thus contaminated with oil, then I would leave that alone. I would however change the oil, as it might have taken some hit sheered the polymers.... I say might. The oil would also have transported bad stuff away as a result of the overheating. It is a cheep way to buy insurance, along with the filter. The rattle at shut down, would lead me to check the valves as well. Just to be sure. If the motor sounded normal prior to shut down, I would forgo the valve check. Then start it up, but not before you spin the heck out of that fan with compressed air. As the engine was running when you shut it down, I see no need for a tear down. Even the valve check is just to be safe. They dont really move the tolerances at overheating, but it is a quick thing to check. That is the way I would proceed. Hopefully all will be well. Let us know how it goes.
That sounds a lot better than I thought. I was confused by your first coment on the coolant, then I realized you didn't get my reasoning. I wasn't worried about a blown head gasket (should I be?!?), I just thought the cooling system wasn't working properly. As I said, I had just freed up the fan - I couldn't check it at the time without burning my hands. I didn't notice if it was running, either. But I think it is a fair assessment that the cooling system should have prevented this if it were working properly - especially with the relatively cool ambient temperature. Thus I think I need to go a step further and make sure there is no air in the cooling system causing my problem.
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Old 03-03-2013, 08:24 AM   #59
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That sounds a lot better than I thought. I was confused by your first coment on the coolant, then I realized you didn't get my reasoning. I wasn't worried about a blown head gasket (should I be?!?), I just thought the cooling system wasn't working properly. As I said, I had just freed up the fan - I couldn't check it at the time without burning my hands. I didn't notice if it was running, either. But I think it is a fair assessment that the cooling system should have prevented this if it were working properly - especially with the relatively cool ambient temperature. Thus I think I need to go a step further and make sure there is no air in the cooling system causing my problem.
Yes, your cooling system should have prevented this. Two things in that system could have failed, as you pointed out, Inoperable fan, or air in the system. As you stated " by a spec of dust" you are correct that the fan have a tendency to fail to rotate. I found, by living in the desert, that if you wash the bike on a regular basis, and blow the fan rotating with compressed air, you will have no issues, no matter how dirty you ride.... Mine was seized once, before i did the washing. Checking for air in the system, is certainly not a bad idea, but the way you spelled it out, it sounded more like an inop fan.
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Old 03-03-2013, 02:48 PM   #60
JoelWisman
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Quote:
Originally Posted by Mongo357 View Post
I just made a little mistake that has me keenly interested in this thread. I started my 800 up to let it warm up before heading home, then got distracted. It was running for about a half hour. I thought it would be fine, since I just spent a lot of time getting the cooling fan freed up a week before. Also it was maybe 55 Deg F at the time. But when I checked on her, she was totally overheated - temp gauge was maxed, warning lights, etc. I seem to remember hearing the rattling like Joel is describing. I shut the bike down right away, and could hear the coolant boiling.

I let her cool down, and made it home. I plan to leave her parked until I can change the oil, flush the radiator, and have another look at that damn cooling fan. Then I will start her up and listen closely to the engine. Is there anything else I should do? Unfortunately taking her to a dealer isn't an option right now. Is there any way to upgrade the cooling fan? Seems like it can't overcome the smallest speck of dust.
Do change the oil but don't worry about changing the coolant. However you ABSOLUTELY do want to know how much coolant is in the system and you cant tell from the catch tank. Wait for the engine to completely cool, then remove the radiator cap and very slowly add coolant, se how much it takes. If it takes 1/8 gallon or less, your probably okay. If it takes more, look for melted plastic or hoses on the outside of the engine and realize there may be melted plastic on the inside of the engine such as timing chain guides and bump stops.

This could be minor or require a complete engine tear down.

At best, warming up the engine by idling does no good. At worst it increases wear or in cases like this can destroy the engine. Your not the first, I have replaced more engines because people were warming them up then all other causes combined.

My fingers are crossed for you, good luck and hope all turns out well.
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