2008 F800GS Unusual Noise After Service

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Hi all, wondering if any of the many experts on here has come across this noise before (https://youtu.be/uj93ZZAoE44), it sounds like pulsating air.

I changed oil and filter a week ago and this noise has appeared not long after it. It's consistent and does not increase or decrease with throttle or speed.

I had a quick run through the bike after work this evening to investigate, I noticed some cracking on the throttle valve assembly, you can see it on the video, however if this was the cause of the noise, I would expect it to change on increased air intake so ruling that out.

Any thoughts on root causing this? process of elimination...

2008 BMW F800GS 0219
bike has 44,000 miles and very well maintained through its life.


All the best,
Paul
 
HI,
My guess is that cracked hose is your problem, it needs replacing anyway. you could do a temporary bodge with some silicone sealant and see if it improves
 
Yeah it isn't in good condition, trying to get a new part will take some time to be delivered, i'll try patch it up and see if that reduces that sound when root causing the issue further at the weekend.
 
It's a bit odd, right enough. That is the inlet manifold. IIRC, it sits below the throttle bodies. If that is admitting air at that rate, it should really mess with the way the bike is running (i.e. air/fuel mixture should be all wrong - way too much air ingress post mixture ) This bike seems to run quite well.

In any case, changing them is a really good idea anyway and they should not be too expensive... I'd start there too.
 
Yeah that is the odd bit, the bike was running ok and there was no observable difference when increasing revs either. I had experience before with another bike causing issues due to an air leak into the carburetor and it was groggy and spluttering on and off. As of today, the bike is now running odd at idle as if it's going to cut out. My new rubber boots arrived so i'm going to replace them, should fix it hopefully.
 
Don't see it mentioned anywhere in the above thread posts, but I have had a really poor idle on a F8GS when the idle stepper motor got out of sink due to oil/water contamination in the airbox.

You'll need a GS911 or connection to the motherships computer to check and sort this if it is whats wrong - the stepper motor need to be re-synced so it knows what position is fully open and what is fully closed.

SteveT

:cool:
 
SUCCESS! I replaced both rubber boots that were badly degraded and cracked, however the potential root cause is most likely the idle hosing which was degraded and split after dismantling the bike.

This would explain why it was chuffing on idle and did not increase on increased throttle.

It took a long time to rectify the issue with parts coming in from different countries but glad to have it fixed.

The bike is running terrible fuel economy now, it may take some time for the CDI to optimize, i'm wondering if I should borrow a mates diagnostic GS-911 and do some checks on that, like the calibration step you've mentioned @SteveT it'll be good to test it out. I came across that option the last time I was using the GS-911.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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