1150GS not running right..

[Bakas]

Hi all, I've run out of ideas what can be wrong with the bike and need help figuring it out.

Bought the neglected GS last year from Germany, where it was parked on the street for a mere 5-6 years. Decided I want a challenge and I've got one.

Things I did:
Clean the tank, new fuel pump and hoses, injectors cleaned.
New O2 sensor, new temp sensor. new sparks and cables.
TPS set throttle bodies synced up, valves adjusted.

The bike starts ok and runs sweet until it warms up to 2 bars and then suddenly something changes and bike starts surging, sputtering and jittering while trying to keep steady RPM. If I give it a good twist it goes, but refuses to run steady in the 2.5-4.5 RPM range.

Really want to find out whats wrong with it, maybe someone will have ideas?

Cheers!

 

[Tristafarian]

Dislodged throttle cable on left hand side?


Sent from my iPhone using Tapatalk

 

[hops]

Dislodged throttle cable on left hand side?


Sent from my iPhone using Tapatalk

Unlikely, it would be running rough from the start if the cables were unseated. Did you replace the fuel filter & the 'U' shaped pipe inside the tank when you did the pump? Is it a single or twin spark? Other things to maybe consider depending on year, ignition coil, fuel pressure regulator, ignition hall sensor.

 

[oblertone]

This ...

...

 

[Tristafarian]

...

I managed to dislodge mine on the other end. Can’t remember the technique to rectify it but it’s in the forum somewhere.


Sent from my iPhone using Tapatalk

 

[Riceburner]

Hi all, I've run out of ideas what can be wrong with the bike and need help figuring it out.

Bought the neglected GS last year from Germany, where it was parked on the street for a mere 5-6 years. Decided I want a challenge and I've got one.

Things I did:
Clean the tank, new fuel pump and hoses, injectors cleaned.
New O2 sensor, new temp sensor. new sparks and cables.
TPS set throttle bodies synced up, valves adjusted.

The bike starts ok and runs sweet until it warms up to 2 bars and then suddenly something changes and bike starts surging, sputtering and jittering while trying to keep steady RPM. If I give it a good twist it goes, but refuses to run steady in the 2.5-4.5 RPM range.

Really want to find out whats wrong with it, maybe someone will have ideas?

Cheers!

Sounds to me like something electrical breaking when hot - ie a poor connection or weak wire breaking down. Happens a lot in old magnetos (I currently have similar symptoms on a BTH mag fitted to a JAP engine), but not sure what it would be on a modern bike - a coil maybe? Is it a twin or single spark? Normally if the Coil caps on the primary plug are breaking down the secondary is enough to keep the bike going (they're run off a separate coil under the tank), but if the secondary is also weak that might cause the issues you're describing.

 

[Bakas]

Dislodged throttle cable on left hand side?


Sent from my iPhone using Tapatalk

I wish it was as easy at this..

 

[Bakas]

I have gone the easy route and just used a piece of submersible hose. I doubt its the problem as I get 6-8 bar pressure from the pump so it shouldn't be starving for fuel. Its a single spark. Im looking for ignition coil to make a swap test at the moment. Where does the fuel pressure regulator live on the bike? Ive put a used hall sensor on, should probably slice it and rewire?

 

[Bakas]

Unlikely, it would be running rough from the start if the cables were unseated. Did you replace the fuel filter & the 'U' shaped pipe inside the tank when you did the pump? Is it a single or twin spark? Other things to maybe consider depending on year, ignition coil, fuel pressure regulator, ignition hall sensor.

I have gone the easy route and just used a piece of submersible hose. I doubt its the problem as I get 6-8 bar pressure from the pump so it shouldn't be starving for fuel. Its a single spark. Im looking for ignition coil to make a swap test at the moment. Where does the fuel pressure regulator live on the bike? Ive put a used hall sensor on, should probably slice it and rewire?

 

[hops]

I have gone the easy route and just used a piece of submersible hose. I doubt its the problem as I get 6-8 bar pressure from the pump so it shouldn't be starving for fuel. Its a single spark. Im looking for ignition coil to make a swap test at the moment. Where does the fuel pressure regulator live on the bike? Ive put a used hall sensor on, should probably slice it and rewire?

Follow the fuel lines from the injectors back to the middle of the bike and it sits in a little recess above the gearbox and under the air filter box if memory serves me right. #2 in the diagram

 

[otruk]

Could it be worth looking at the air take off on the bottom of the throttle bodies, if they have a split.

 

[kingo]

Try changing coil sticks

 

[Bakas]

Follow the fuel lines from the injectors back to the middle of the bike and it sits in a little recess above the gearbox and under the air filter box if memory serves me right. #2 in the diagram

This could be the problem since the bike stood still for 6 years or so, I need to look at the valve, thanks.

 

[papa_jop]

Try measuring ignition coil, cold and warm (ie. directly after noticing trouble).
Does the rev counter jump around? Hall effect sensor, or rather the cables to it.
Steel tank? Less likely possibility is that some tank liner came loose after your cleaning of the tank. This can block the pump strainer.

 

[Bakas]

Try measuring ignition coil, cold and warm (ie. directly after noticing trouble).
Does the rev counter jump around? Hall effect sensor, or rather the cables to it.
Steel tank? Less likely possibility is that some tank liner came loose after your cleaning of the tank. This can block the pump strainer.

How can I measure ignition coil? Will look into the hall sensor cables if the fuel pressure reg will not fix things. It is a steel tank that lining completely fell to bits. I have cleaned the tank and installed new pump, hoses filters the lot

 

[Bakas]

This could be the problem since the bike stood still for 6 years or so, I need to look at the valve, thanks.

I have removed the valve yesterday, any way to check if its good or just order another 100$ part?

 

[papa_jop]

How can I measure ignition coil? Will look into the hall sensor cables if the fuel pressure reg will not fix things. It is a steel tank that lining completely fell to bits. I have cleaned the tank and installed new pump, hoses filters the lot

Ignition coil:
Measure primary side between terminal 15 and 1: ~0,5 Ohm
Measure secondary side between terminals 4a and 4b: ~13 Kohm

Are you sure you got all the failing tank liner out of the tank?

 

[Ian J Hartley]

I have removed the valve yesterday, any way to check if its good or just order another 100$ part?

Doubt it, you can bypass the fuel pressure valve, by just disconnecting the fuel return line to the tank. That way the pressure in the manifold to the injectors is at the maximum pressure that the pump can put out. The engine management can cope with this by cutting the duration of the injectors when in the closed loop.

All the pressure regulator does is maintain a constant pressure in the manifold, by passing excess fuel back to the tank.

Think of it as:-
P1 = pump pressure.
P2 is injector manifold pressure.
P3 is return fuel pressure.

P1 = P2 + P3 if you remove P3 then P1 must equal P2. Assuming there are no leaks.

 

[Bakas]

Ignition coil:
Measure primary side between terminal 15 and 1: ~0,5 Ohm
Measure secondary side between terminals 4a and 4b: ~13 Kohm

Are you sure you got all the failing tank liner out of the tank?

Not being an electrician Im puzzled as to how to measure Ohm's.. Is there any youtube link?

Very sure, I have painstakingly removed most of it ant the 2 filters in the tank are doing their job to not let any small bits be sucked in.

 

[DrFarkoff]

If you build a test rig leave the injectors connected to block off the outlets

Feed air pressure to the lower pipe the gauge should be on this end

Somewhere about 2.2 or 2.4 bar the fuel pressure regulator should release excess pressure and blow out the return line

If it is any where below 18psi it needs replaced or cleaned

Also invert the injectors and tap them down firmly on some hard wood and see if you knock any paint flakes out ??

I have had success with flushing the pressure regulator with air pressure

Is the pump in the tank capable of producing 28 PSI