R1100GS Misfire - Help Needed Please

[Roger 04 RT]

The GS-911 can read and clear error codes on the R1100GS/RT/R but it can't read realtime sensor values. I don't know what the dealer equipment can read.

 

[JoePap]

I'm back from SBW Motorrad in Welwyn Garden City. They suggested a few issues that might be contributing to the problem but were at a bit of a loss. Their diagnostic testing machine turned out not to be compatible. My R1100GS is older than they're used to dealing with. They don't keep spares on the shelf for such old bikes any more, which was a bit disappointing.
The mechanic reported some fraying in the throttle cables. Not necessarily a cause of the fault but he recommended changing them and thought the throttle bodies would balance better once that's done. They quoted £200 to change the throttle cables.
His compression tester indicated 130psi on one cylinder and 150 psi on the other, which is different from what I got from mine. Mine said 165 psi on both.
He said
The cam sounds a bit worn.
One of the throttle bodies is a bit worn.
He cleaned up the throttle body mechanisms. Probably just sprayed 'em with carb cleaner. I don't think he disassembled them.
It cost £63 for that work but I didn't fancy going any further with them. It could easily turn to a money pit and I'm not convinced any of those issues are the root of the trouble.
The mechanic suggested adjusting the CO potentiometer, so I'll have a go at that.
If anyone can recommend a firm that specialises in early oil-heads, please post the details.
Thanks.

 

[JoePap]

Sorry, I should've said if anyone can recommend a firm near to Watford, Hertfordshire, that specialises in early oil-heads, please post their details. Thanks.

 

[Karlread]

Steve Sriminger in Sleaford would definitely be worth a shout, a lot of bods on this forum and on bikers oracle have used him for broken gearboxes, he is a proper engineer and they race BMW's look on Scriminger engineerings website and their facebok page. He is very enthusiastic, works for the love of the bikes. He did the gearbox on my R1100RS, I realise it is a trek but it may well be worth the 3 hour ride if you can nurse it up there.
Hope you get it sorted, I purchased an R1100RS in February and unfortunately had to sort loads out on it. One thought though, on my bike there are a bunch of plugs/connectors on the nearside by where the rear sub frame fits. I would check them as I too had a problem with running and it was a corroded connector not putting enough current through. Worth a try.....

 

[flatdog]

Sorry, I should've said if anyone can recommend a firm near to Watford, Hertfordshire, that specialises in early oil-heads, please post their details. Thanks.

Try Steptoe, he is in south london and well worth having a chat to, plus he's closer.

I've used scrimingers in the past for gearbox / diff overhauls and they are great, but for bigger type jobs than what you are facing (distance wise = convenience)

 

[Roger 04 RT]

I'm back from SBW Motorrad in Welwyn Garden City. They suggested a few issues that might be contributing to the problem but were at a bit of a loss. Their diagnostic testing machine turned out not to be compatible. My R1100GS is older than they're used to dealing with. They don't keep spares on the shelf for such old bikes any more, which was a bit disappointing.
The mechanic reported some fraying in the throttle cables. Not necessarily a cause of the fault but he recommended changing them and thought the throttle bodies would balance better once that's done. They quoted £200 to change the throttle cables.
His compression tester indicated 130psi on one cylinder and 150 psi on the other, which is different from what I got from mine. Mine said 165 psi on both.
He said
The cam sounds a bit worn.
One of the throttle bodies is a bit worn.
He cleaned up the throttle body mechanisms. Probably just sprayed 'em with carb cleaner. I don't think he disassembled them.
It cost £63 for that work but I didn't fancy going any further with them. It could easily turn to a money pit and I'm not convinced any of those issues are the root of the trouble.
The mechanic suggested adjusting the CO potentiometer, so I'll have a go at that.
If anyone can recommend a firm that specialises in early oil-heads, please post the details.
Thanks.

Don't bother adjusting the CO pot, it doesn't affect higher loads. See if you can find someone with a spare TPS for a trial swap, or maybe someone who'd loan you theirs for a trial.

One thing you could try so to make sure the throttles come off the stops at the same moment and reach WOT at the same moment.

 

[MikeO]

Hi Joe,

I'm pretty sure I have a TPS spare in the garage. It'll be off an 1150, but they are the same part number - let me know if it would be of any use to you.

Cheers,

Mike

 

[Roger 04 RT]

I went back and reread the thread.

1) It is probably time to measure each injector's flow rate and get them cleaned.

2) Since you get 2liters/minute on the fuel return, the fuel pressure is probably okay but measuring fuel pressure on the high pressure (lower) line should be done.

3) If you can get a spare TPS, that is still worth trying.

4) Double check that the throttles come off the stops at the same moment and reach WOT at the same moment.

On this list I'd check 1) (the flow rate) and 4) next.

 

[JoePap]

I've removed the fuel pump assembly. The paint's peeled off the inside of the tank. Probably the ethanol and other new detergents in the fuel. The gauze filter is intact. I've ordered a new fuel filter. I doubt that'll sort it 'cos the fuel flow rate was good at 2 Litres per minute, still best to change the filter, while it's off. All the hoses and clips are OK and none of the hoses had any blockage.
Once the new fuel filter arrives and the fuel pump assembly's re-installed, I'll do a flow test on each injector. I'll send them for cleaning.
Yes the throttles come off the stops at the same time and reach wide open throttle at the same time.
I've bought a color tune spark plug and am looking to borrow an exhaust gas analyser.
Mike, thanks for the offer to borrow your spare TPS. Mine seems to give all the right signals but a bit further down the line I might take you up on that kind offer.
The bike is worse than ever. If I yank open the throttle in neutral, it'll cough and splutter and won't rev. I think it's not getting enough fuel and want to try to verify that with the color tune and by monitoring the exhaust gasses.

 

[DrFarkoff]

Sorry but I think you are barking up the wrong tree you are focussing on one area rather than diagnosing the "actual" fault

You could save yourself a big head ache and take it to Steptoe

Before you do anything Else I would change the TPS then the Coil / leads / plugs

P.S. have you been starting this bike a lot and NOT running to working temperature ???

If so Change the plugs Before you do anything else just use NGK BKR5E-11 they are as cheap as chips if you screw them up again

The other ones I use are ZFR5A-11 (its a projected nose one I have used quite a few times in My R1100GR hybrid thingy

Basically what happens is that the plug does not get hot enough to burn off the "deposits" from not being run to temp the deposits are carbon

Sparks track across the surface rather than jump the air gap and you lose spark efficiency and "bad" sparkplugs are especially known to fail under load

 

[DrAlf]

Steptoe is very good and Scriminger is supposed to be excellent but it's also well worth considering MotoScot who are very local to you (and me) - just off the M1/A5 junction near Luton. He rebuilt my 1150 a few years ago and did an excellent job. Well worth giving him a call:

http://www.motoscot.co.uk/

Does the 1100 have a fuel pressure regulator and could this be the issue I vaguely remember having a nightmare troubleshooting rough running on my 1150 a few years ago and eventually traced to a faulty FPR?

Good luck

 

[JoePap]

No mine's a 1994 R1100GS, there's no fuel pressure regulator. I changed the fuel filter and checked all the hoses and connections before re-assembly. All fine. The fuel pressure from the pump is 80 psi but seems to be much lower in normal operation, the feed back to the tank stopping the pressure from building up. I couldn't get a reading with the fuel circulating. Is that normal?
I've watched the combustion through the color tune plug and I can see the misfires and coughs as bright white flashes interrupting the normal blue of good combustion.
I've removed both injectors to send away for a test and clean. If that doesn't improve things I'll look again at the Throttle position sender, which is definitely functioning as it should. Perhaps the voltage outputs from the TPS aren't making it through to the ECU. I've tried another ECU and wiring harness. I might try opening up one of the ECUs go get readings from it's board.
It would be easier to take it to a mechanic but it's interesting to keep trying things. Thanks for the tips and advice. I've ordered another new set of plugs but don't think the plugs are the problem having replaced them already.

 

[Roger 04 RT]

No mine's a 1994 R1100GS, there's no fuel pressure regulator. I changed the fuel filter and checked all the hoses and connections before re-assembly. All fine. The fuel pressure from the pump is 80 psi but seems to be much lower in normal operation, the feed back to the tank stopping the pressure from building up. I couldn't get a reading with the fuel circulating. Is that normal?
I've watched the combustion through the color tune plug and I can see the misfires and coughs as bright white flashes interrupting the normal blue of good combustion.
I've removed both injectors to send away for a test and clean. If that doesn't improve things I'll look again at the Throttle position sender, which is definitely functioning as it should. Perhaps the voltage outputs from the TPS aren't making it through to the ECU. I've tried another ECU and wiring harness. I might try opening up one of the ECUs go get readings from it's board.
It would be easier to take it to a mechanic but it's interesting to keep trying things. Thanks for the tips and advice. I've ordered another new set of plugs but don't think the plugs are the problem having replaced them already.

Joe, There is a fuel pressure regulator, in front of the airbox, under the battery. It is set to 43.5 psi. When you put a fuel pressure gauge in the lower line on the right side of the frame going to the plastic hoses to the fuel distributor it will show about 43 psi if the battery voltage is at 13.8 volts. If the bike isn't running, the pressure will be a little lower due to the lower battery voltage.

 

[Karlread]

I wonder if Roger RT 04 has hit the nail on the head here, this is a great read for all of us who still have an R1100 bike, sadly though at the misfortune of the OP. This is working out to be like one of those inspector Morse episodes, you think you know what/who the cause was then it is something completely different. I can only say that the OP has the patience of a saint!

 

[JoePap]

HI Roger
Your idea about the fuel pressure regulator is a useful lead.
I'm getting 80psi on the return feed measured when the bike is not running.
I've ordered a y-piece so I can monitor both sides when the bike is running and the fuel is returning to the tank as normal.
I'd like to measure the pressure at each injector, but I'd need a special T piece. Does anyone know if one's available? It'd need to have a male and a female fuel injector connector.
It could certainly be the regulator not delivering enough pressure and flow so the injectors get starved at high delivery. That'd be consistent with the fault.
The regulators a bit awkward to get to. It needs the rear subframe lifted and the airbox removed. I've done it before. I'd like to diagnose it before taking the old one out and having the cost of buying a new one to try.
Thanks Roger.

 

[Roger 04 RT]

HI Roger
Your idea about the fuel pressure regulator is a useful lead.
I'm getting 80psi on the return feed measured when the bike is not running.
I've ordered a y-piece so I can monitor both sides when the bike is running and the fuel is returning to the tank as normal.
I'd like to measure the pressure at each injector, but I'd need a special T piece. Does anyone know if one's available? It'd need to have a male and a female fuel injector connector.
It could certainly be the regulator not delivering enough pressure and flow so the injectors get starved at high delivery. That'd be consistent with the fault.
The regulators a bit awkward to get to. It needs the rear subframe lifted and the airbox removed. I've done it before. I'd like to diagnose it before taking the old one out and having the cost of buying a new one to try.
Thanks Roger.

Joe, 80 psi on the return feed may or may not be a problem. If you blocked return to the tank, 80 psi is probably what you'd get. You really need the "t" so that fuel is flowing and the "t" needs to be in the supply (lower) line. In the return line you shouldn't measure any pressure.

If the regulator is stuck open, as you're saying, pressure could be low on the supply side and that would be a problem.

 

[DrFarkoff]

Did you check that the throttle cables are not hanging and keeping the throttles open

I've just spent a couple of hours adjust ing and readjusting and sorting out an 1150 that was running like a bag of schite into a rippy snorty thing

Whilst I was working on it once at temp but revving at 1300 with big brass screws fully in

I could hear it farting and banging in the exhaust with an intermittent misfire

Slackened throttle cables so that the throttles rest on their stops and started all over again and Now the misfire is gone and its quite snappy on the throttle now

Just another Idea for the pot as you guys seem very fixated on the fuel pump/pressure relief valve side of things

 

[JoePap]

The problems not fixed so I've sent away the injectors for testing and overhaul.
I've changed the throttle cable (mine is '94 bike so it has one long cable that includes a link to the second throttle body).
The fuel pressure on the feed side of the circuit turned out stay good when running 45psi and fuel is flowing back to the tank at 2 litres per minute so it doesn't seem to be a fuel pressure regulator problem. It was a good idea and worth checking though.
I adjusted the idle screws but found on the right hand throttle body I can screw the idle screw right in and it still ticks over OK. There is a bit of movement in the throttle body shaft so perhaps a little air is leaking in when the throttle's closed.
I made sure both cables let the throttles fully close and open at the same time. Throttle balancing was still proving a bit tricky but I've decided to get the injectors done first and then balance the throttles.
My only other thought is to advance the timing to see if that helps.

 

[Timolgra]

I adjusted the idle screws but found on the right hand throttle body I can screw the idle screw right in and it still ticks over OK.

Throttle balancing was still proving a bit tricky

What exactly do you mean by a bit tricky?

 

[Roger 04 RT]

...

My only other thought is to advance the timing to see if that helps.

The R1100 and R1150 have complex timing curves, a X-Y map about as large as the fuel table. Because of that I would check the timing to make sure it's set as it should be but I don't see how altering it would help.