Rough running at high speed GSA 2008.

commandoallan

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Evening All,

I have had a rough running GSA 2008 since I purchased it, an intermittent problem at high speed around 4000-5000 RPM. Assumed it was because of a fuelling/ air problem but others stated coils. I got rid of the K&N air filter and cleaned the sensor in the air box for a little improvement, I then had two coils and all plugs replaced by my local BMW dealer who stated one was shot and the other an incorrect fitment, the bike ran good for around a month then the issue returned.

I have now changed the main fuel pump (LHS) and the bike seems stronger (maybe imagination??) but the issue is still intermittently there. I am now thinking of changing the secondary pump on the RHS and the pressure regulator and looking at the breather hose before getting BMW to look at the bike again.

I could do with a little info on the pump for the RHS, is it the same model as for the left? And could the issue be with the pressure regulator and/ or breather hose....Where the f...ck is the breather hose?

Any opinions and advice would be greatly received.

Many thanks.
 
The rhs pump is only for transferring fuel to the left side of the tank. It is a venturi, no moving parts. Return fuel from the main pump is used to create a suction and lift fuel from rhs tank to lhs tank.

If you reduce revs, does the problem immediately stop? Is it like a misfire?

Help from someone nearby with a GS911 code reader would be good if poss.
 
Thanks for the answer,

I have previously used my GS911 but no fault codes for any of this. No misfire but a general sense of lack of power when this happens although I can maintain speed, it sounds rough/ raw and the bike seems to be struggling which is why I initially thought a fuel issue.... Maybe ties in with lower fuel within the tank (1/2 tank or less) the majority of the time but not always.

This only happens at high speed and the problem does not stop when I reduce the revs, no issues at low speed at all.
 
Maybe fuel starvation caused by blocked breathers? Try riding with fuel cap open/ajar for a bit? There are breathers next to the fuel cap for the tank and I think on the RHS theres more?
I assume the TBs are balanced and valve clearances are all good?
As Bin Ridin stated the other 'fuel pump' is a weird non moving part that only transfers fuel from one side of tank to the other so it doesnt supply fuel to your injectors it deals with the non used return fuel.
 
Thanks, will have to have a look at the breathers and try the open cap for a couple of trips.

New plugs (2 x new sets) one set by me and the other two weeks later along with the two coils by BMW, valve clearances good as done by me with my major service. Still thinking of the weird fuel pump and transferring of fuel an issue?
 
RHS pump does not feed injectors, just transfers fuel to use tank up evenly. Why are only two coils changed so far, or am I misreading?
 
BMW looked at the bike and stated only two coils needed replacing, am thinking of changing the other two but unsure if this is the issue. Thought I may go to BMW again to re assess but I could always buy two more and fit myself?
 
As long as you have one new coil each side, I would tend to park the idea of replacing the other two coils for now, if they have a clean bill of health from your dealer.

So, if it aint sparks, it could be fuel delivery. You don't say what happens in say first/second gear at high revs but relatively low speed. Are you still hitting a wall & then not able to ride through that 5k rev range?
Generally, the symptoms point towards a lack of fuel pressure - did your dealer look at the fuel ditributor/regulator & injectors or just the coils? Presumably the O2 sensors checked out OK.

Just a couple of random thoughts; are the intake trumpet affairs that feed the airbox clear. I've known guys find them blocked with debris, cleaning rags & even mouse nests after a winter lay-up. Then, what pipe are you running? - is the exhaust clear or is the can breaking up internally & restricting flow.
 
This issue only happens at fast speed from around 4000-5000 RPM when generally I am on an A road, no issues at any rev range in low gears at lower speed. Not hitting a wall as such but the bike strains and feels starved of power/ rough at 70MPH sometimes. The bike can go all the way through the rev range at all speeds but just feels starved intermittently (I have an 2 hour commute each way).

Dealer did not look at anything other than the coils x 2.

The airbox is clear, I have an aftermarket endcan but the problem was there before the endcan was put on and there is no difference since fitting it. I was thinking of the regulator and breathers as I have changed the fuel pump. I have also just bought two secondary coils to fit and hope this may fix the problem?
 
BMW looked at the bike and stated only two coils needed replacing, am thinking of changing the other two but unsure if this is the issue. Thought I may go to BMW again to re assess but I could always buy two more and fit myself?

Test them, it's simple enough..

Unplug the coil connectors on both the bottom secondary coils and see if the bike runs on both side on just the main coils.

If all good then do the same test on the secondary coils, i.e. reconnect the secondary coils and disconnect the main coils.
 
Test them, it's simple enough..

Unplug the coil connectors on both the bottom secondary coils and see if the bike runs on both side on just the main coils.

If all good then do the same test on the secondary coils, i.e. reconnect the secondary coils and disconnect the main coils.

Thanks Steptoe,

Now this is a really stupid question.....But how do I know if the bike is only running on one cylinder????:blast
 
Thanks Steptoe,

Now this is a really stupid question.....But how do I know if the bike is only running on one cylinder????:blast

You'll soon know....

Disconnect both coil connection plugs on one side and start it up to give you an example.. :D
 
This is all fine until both coils are failing then all you get is confusing symptoms.

A genuine misfire will cause the engine to run rich as the unused oxygen fools the ECU into adding more fuel when in reality the fuel moisture is fine.

Try a fast run with secondaries disconnected, then again with them connected. If possible borrow a known good pair. I suspect it will make no difference as they are there to clean up emissions - only really do anything useful at low revs.

If you have an IR thermometer, check that you have the same temperature in both exhaust headers? Run the engine above 1500rpm to rule out idle steppers. If one side is low you'll need to get that sorted before going for fast road tests.
 


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