Rough feeling drive train

[ILMV]

G'day all,

Of late I've been a little off with my 09 F800GS, I just don't feel I'm riding it all that well and it's messing with my head a little... unsure if it's me or the bike.

My primary issue is the drive train feels rougher than I imagine it should be.

When I'm coming off the gas I get a jolt through the drive train, usually I've got to take a small hit of confidence clutch™ to smooth things out.

Here's a couple of facts:

- Rear wheel bearings aren't in the best shape (replacing soon)
- Cush drive rubbers are in good condition, no perishing there
- Recent discovered I wasn't adjusting the chain correctly (was on center stand, not side stand)
- Diff between tightest and loosest bit of the chain probably measures ~10mm
- Chain only 6 months / few thousand miles old
- I have the accelerator module installed, have from day 1 (42k miles now)
- Running an Akro can without the silencer

Can anyone provide a bit of insight here? Things to try for me or the bike would be super helpful.


Cheers

 

[kyojitsu]

When you say jolt what do you mean exactly? Do you mean a sudden deceleration or jerkiness? Transmission lash is usually a problem when you're on the gas or re-engaging the clutch and getting a lurch or clunk. I'm inclined to think this is more of a fuelling issue or throttle travel issue so perhaps the accelerator module is the culprit I.e. developed a fault? Can you remove it temporarily to eliminate that issue?


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[ILMV]

Hey kyojitsu,

Jerkiness when coming off throttle sounds about right, it seems that unless I come of the gas in a certain manner (can't explain) I get what I can only describe as the kind of slap you'd get from a slack chain.

To counter, when I'm giving it full beans it pulls nice and smoothly.

I have noticed of late that the bike (definitely when cold, will check when warm) the bike cannot hold revs around 2.5k - 3k, when I'm holding the throttle dead still the revs will fluctuate by 500rpm.

I'll remove the accelerator module to see how that changes things.

The bike is on ~42k miles, don't think I've ever had a fuel filter change.

Additionally, cleaning injectors? I did a tank of redex a month or to back... any concern with these last two points of fuel starvation (to a degree) when not on throttle?

 

[kyojitsu]

Might be worth checking the throttle position sensor - does sound like a throttle issue though. May be worth getting codes read too especially if it's spoiling your enjoyment of the bike.


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[thomo57]

Do you know anyone with a GS911 ? A diagnostic scan may throw up a clue


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[ILMV]

Thomo I don't but I'd love to get my hands on one... would be good to know what the bike is thinking.

 

[Packer]

If you were setting the chain to spec on the centre stand once back on its wheels it may have been over tight and stretched. That could perhaps make the transmission feel a bit coarse and if it didn't stretch evenly it would be worse.

 

[Gerry atric]

BTW I have read differing views on whether to adjust the chain on side or centre stand, what's the view on that?

 

[thomo57]

As not all bikes have the optional centre stand, BMW manual states the adjustment should be carried out on the side stand - same goes for checking the engine oil level.


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[ILMV]

Thanks all for your input.

First of all, removed the accelerator module and things seem smoother! Although, I'm pretty sure that's placebo.

Good point Packer, possible that not using the sidestand for the chain tensioning has messed with it. I'll give it some miles to figure out if it needs replacing or not.

 

[AberdeenAngus]

When you say difference between tightest and loosest bit of the chain is 10mm - what do you mean?

Sounds more like fuelling but a couple of quick checks of the mechanicals to be sure......
Get it up on the centre stand and rotate the back wheel.
Is the play on the chain consistent all the way round?
Do the links pull away from the back of the rear sprocket by equal amounts all the way round?
Take the plugs out and pop it in gear.
Again, rotating the back wheel, is everything smooth?
Turn the back wheel back and forth - any significant slogger?
Is the chain well lubricated?
Are the sprocket teeth in good nick?