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Old 12-16-2012, 07:04 AM   #1
Rabbitson OP
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BMW F800ST timing

Hi there,

I recently bought a rattling F800ST from 2008 and I am interested in making it run properly again. The rattle came from the top end and did not seem to matter if it was in gear or not.

The first job was therefore to open the bike and take a look.

With that in mind, I've removed the cam covers and I can see that the timing marks do not seem to be lined up correctly. (i.e. The EX on the front camshaft does not seem to want to line up with the IN on the rear one as per the service manual)

Looking down the inlet manifold I can see that the valves (at least on the inlet side) do not seem to be damaged, so I am wondering what the easiest way to reset the timing correctly would be? Is it absolutely necessary to drop out the engine, or is there someway to reset it without doing that?

Thanks for any advice.
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Old 12-16-2012, 07:12 AM   #2
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Quote:
Originally Posted by Rabbitson View Post
Hi there,

I recently bought a rattling F800ST from 2008 and I am interested in making it run properly again. The rattle came from the top end and did not seem to matter if it was in gear or not.

The first job was therefore to open the bike and take a look.

With that in mind, I've removed the cam covers and I can see that the timing marks do not seem to be lined up correctly. (i.e. The EX on the front camshaft does not seem to want to line up with the IN on the rear one as per the service manual)

Looking down the inlet manifold I can see that the valves (at least on the inlet side) do not seem to be damaged, so I am wondering what the easiest way to reset the timing correctly would be? Is it absolutely necessary to drop out the engine, or is there someway to reset it without doing that?

Thanks for any advice.
Does the repair manual state that the engine have to be removed.....????? Just locate the top dead center, via sight hole....( facilitate this a bit easier with the spark plugs removed, and put the bike in 6 gear, and roll the rear to find the TDC) then check the marks on the cams. If they are not lined up then you need to remove the cam lobes, and readjust. Need to remove the ACCT ( Automatic Cam chain tensioner) as well. That's what comes to my mind.... But I have not done it on this motor.
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Old 12-16-2012, 07:27 AM   #3
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Hi Erling,

I do not know if the manual says the engine needs to be dropped out, I just presumed that it would be.

If I adjust the timing as you suggest how can I be sure that I don't get the timing 360 degrees out? (probably this is a silly question but I want to be sure)

Thanks

David
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Old 12-16-2012, 07:35 AM   #4
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Are you 100% positive the timing is off? I would be looking at the camchain tentioner before messing with the timing. You say the topend has a rattle. There have been several threads on different forums about high mileage 800's having the rattling noise when the camchain tentioner wears out.

If the timing is actually off (and I doubt it is) by a tooth ya need to ask the question of why? Camchain tentioner shot, camchain stretched, how did it get like that? The chain would have to be stretched a hell of a lot to skip a tooth. If it is then just putting it back is not going to fix it.

If the chamchain is off a tooth and the valves aren't hitting the pistons would the topend rattle or would the bike just run like shit? I would get the most experienced person I could find to take a look att things before doing anything else.
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Old 12-16-2012, 08:40 AM   #5
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If you got the cam cover off, you should not need to remove the engine.

The cams go in 1 way, no 360 out, as long as the timing marks are aligned, you will be good. Since you have the chain rattle it sounds like a stretched chain. It could be a cam installed incorrectly, but it would have to be 1 tooth out. How much is the timing mark off?
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Old 12-16-2012, 10:09 AM   #6
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Whoops

Thanks for the info, it seems that in fact I was too quick in my diagnosis and in fact the timing is correct.




The tappets also seem to be more or less within tolerance so I guess I will check the camchain tensioner next.

Is there anyway to actually check the tensioner is working without just replacing it?

The investigation continues . . . .

thanks anyway for your help up to now.

David
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Old 12-16-2012, 02:34 PM   #7
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I don't think you can check the tensioner other than give it a look over. It has a spring in it, but the primary force is oil pressure.

The manual list a device to measure the chain. It is bolted in place of the tensioner and screwed into the chain/guide. If it goes in too far the chain needs replacing. Not a tool you are likely to find any where but the dealer.

Replacing a chain is a major engine dismantle, but there is an alternative. Go back the Parallel Universe and look in stickys. There is a good pictorial explanation.
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Old 12-17-2012, 01:07 AM   #8
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Thanks

itsatdm, thanks for the information.

That thread http://www.advrider.com/forums/showthread.php?t=727687

is pretty amazing. Just spent about an hour looking through it, very useful indeed. How did we ever get by before advrider!

David
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Old 12-17-2012, 03:44 AM   #9
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Originally Posted by itsatdm View Post
I don't think you can check the tensioner other than give it a look over. It has a spring in it, but the primary force is oil pressure.

The manual list a device to measure the chain. It is bolted in place of the tensioner and screwed into the chain/guide. If it goes in too far the chain needs replacing. Not a tool you are likely to find any where but the dealer.

Replacing a chain is a major engine dismantle, but there is an alternative. Go back the Parallel Universe and look in stickys. There is a good pictorial explanation.
Gary:
Is there a picture of the tool in your version of the manual?
I have Rev. 4 of the manual and there are pictures of the special tools ... but the cam wear tool is not listed.
I know we are up to at least Revision 6 (maybe higher) of the manual now.........
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Old 04-30-2013, 09:42 AM   #10
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Valve Clearances

Ok, so after a few evenings in the garage, I have put a new cam chain on the F800ST, the bike starts and runs so all is good.

I noticed that there was still a tapping in the head so I took it apart again to check the clearances and all but one are fine. However, one of the inlet ones is 1.25mm! That one is out by like a mm! (yes you read it right) I'll try to get a replacement shim for that one but it got me thinking how that situation could come about and whether might be indicative of a problem or damage somewhere?

Any ideas? I have not used the bike at all, I simply purchased it as a high mileage project with no service history.

Thanks for any suggestions

David
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Old 04-30-2013, 10:57 AM   #11
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That's a hell of a lot of slop.............

I wonder if the valve or valve seat is damaged or has a chunk of carbon or other matter holding it open a bit? But you would sure think the bike would run very rough if that were the case.........

Have you run a compression test?

Maybe pull the throttle bodies off and inspect the valve from the back side? See if anything looks amiss?
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Old 04-30-2013, 11:38 AM   #12
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Are you sure you aren't hearing some piston slap? Supposedly early 800 motors could develop slap due to the extremely short piston skirts...
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Old 05-07-2013, 06:30 AM   #13
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Hi there again,

Just managed to get hold of a converter piece for my old compression tester.

A rudimentary test (compression tester in one spark plug hole, push the bike forward in gear) gave readings of 4.0 bar for the right cylinder and 4.3 bar for the left (where the left one has the larger clearance)

I haven't found anywhere to check the figures yet but I'll carry on looking. Probably it would, as you say be a good idea to take off the throttle bodies and see if there's something visibly wrong inside with the valve seating.

DCWineGuy, not sure if it's piston slap or not but I'm working through the easier to fix issues first :)

David
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Old 05-07-2013, 06:40 AM   #14
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Well, the manual seems to state that the compression should be between 10 and 15 bar, so either I'm measuring it in completely the wrong way or the engine has had it!
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Old 05-07-2013, 06:47 AM   #15
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I had to convert to PSI ...

4.3bar is only about 60psi, and while I don't know the spec for the bike I would expect it to be roughly 180 psi given that I think the bike has a 12:1 compression ratio.

So ~4bar is very low....

Did you have the throttle plates all the way open when you did the test?

Also, setting kill switch to "kill" highly recommended ...

On the other hand there's not a dramatic difference in pressure between the two cylinders, so you could likely surmise that the valve IS in fact seating ok....
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