GS 1150 Flat spot between 4-5000 rpm

[katanamangler]

Hi I picked up my GS1150 Adv on Saturday. It has 32k on the clock with service history. One of the previous owners had fitted a Y peice replacing the cat but the standard end can was fitted. The bike came with a remus end can the guy I bought it from had taken it off because he liked a quiet bike. I'm a great believer that loud piped save lives so I asked him to refit the Remus before I picked it up. I had to drive 250 miles home and for the most part the bike ran well a bit of popping on overrun but I put that down to the exhaust system. My real problem was in a higher gear 5th and 6th it seamed to be faltering around 4.5 to 5 thousand revs like it was starving for fuel if you rolled on it did clear and push through eventually but it was a pain in the arse for overtaking. I can t live it like that so I turned to google to find similar experiences.

Confident that it was the the y pipe and remus revolution to fault I tried the spade connector and wire mod on the cat code plug socket ( there was no plug in it. It made no difference ( maybe a bit worse)

I phoned the previous owner and he said he hadn't experienced the problem but he had run the standard pipe. So I changed to the standard pipe and it was still there ( mind you the standard end can was not what I would call an airtight fit should this have a gasket?)

I have lots of older bikes that need regular work and I bought this for the wife and I to do some miles on together I'm none too pleased and need some advice.

 

[Packer]

That sounds like a classic example of coil stick breakdown. Lots of threads on here.

These are very reliable bikes but do need some occasional TLC and regular oil changes.

 

[paz0274]

+1 on the stick coils. Just did mine and it displayed the exact symptoms you describe. When I replaced mine, one was already wrapped in black tape to stop it shorting against the enginecase presumably.

 

[katanamangler]

Thanks for the reply is there anyway to diagnose which stick coil is at fault or is my best bet to replace the pair?

 

[Ian J Hartley]

Thanks for the reply is there anyway to diagnose which stick coil is at fault or is my best bet to replace the pair?

Easy Peasy.

Might be worth checking the plugs first.

Prep the bike by removing any covers etc so you have free unrestricted access to the lower secondary plugs.

Ride the bike until warm (heat can amplify stick coil breakdown)

With the bike warm and idling remove either cylinder lower secondary plug lead. If the bike stops running that side stick coil is stuffed.

If the bike keeps running reconnect the secondary plug lead, and remove the secondary plug lead on the other side.

If the bike stops. That side stick coil is stuffed. If the bike keeps running, then it might not be he stick coils. Reconnect the lower secondary plug lead.

Checking the secondary plug coil is similar only you unplug the low tension (LT) lead to the stick coil. This would help diagnose a faulty secondary plug, or lead, if the fault on only one side. If both sides then the secondary coil pack likely to be stuffed.

All through the checking make sure you limit the amount of time you have HT and LT leads disconnected.

Also your dealing with high voltages, so make sure you haven't got wet hands when doing this test. If you haven't experienced it, a belt of high voltage, hurts, and can be fatal.

If your results are inconclusive, then you might be able to see breakdown if you run the bike in a dark place and look for arcing/sparking. It is not always clear from a visual examination of a stick coil that it is faulty. If its all blistered and corroded, then it's highly likely to be stuffed, but the corrosion gets inside and does the damage, sometimes with little external evidence.

If it is a faulty stick coil, then they are about £70 plus each. Chances are if one has gone, then the other is probably not far away from failure, though this is subjective.

Might also be worth replacing the plugs as well.

 

[Packer]

The usual problem with the stick coils is corrosion. If they don't look corroded they are probably OK. At the price they are you may prefer to identify which is, if either, is faulty and just replace that.

There was about 18 months between my left one starting to fail and the right one following suit. Enough time to refill the piggy bank

 

[Steptoe]

I'm a great believer that loud piped save lives .

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[katanamangler]

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Aye very good but I stand by my philosophy that it's safer to to register on more than one of the sensory perceptions when it comes to being noticed by fellow road users. 25 years of riding has taught me that and I have the scars to prove it. "sorry mate never saw you" is small consolation.

 

[katanamangler]

OK so I followed the recommended diagnosis routine but as I suspected the faulty stick coil didn't show itself. It only seems to happen when the bike is under load and I was unable to simulate this with the bike static.

I couldn't see any obvious shorting marks either so I fell back on my old plug chop routine. I removed the stick coils and wiped them clean and then reinserted them. I then drove the bike to a long piece of road got the bike up to 3rd gear and held it where the misfire was for as long as I could and I then cut the ignition and rolled to a halt. When I pulled the coils I could now clearly see a thin white line along the bottom of the coils next to where the rubber starts. Easily spotted in the bright sunlight I could also see brush marks where someone had painted over the corrosion with black paint , obviously to remedy the situation. The right side was most pronounced but both where minute and difficult to spot.

New stick coils then.

 

[katanamangler]

Oh yeah and ouch £££

 

[Steptoe]

39 years of riding has taught me the opposite.

And i've not one single scar or mark on my body to prove it

Took the noisy pipes off my harley and fitted quite ones.

 

[katanamangler]

Either that or you're lucky not to have met the wrong motorist at the the wrong moment in time . But yes I tend to agree you make your own luck on bikes ( mostly)

In truth I might switch back to the standard can because the rasp is at odds with the character of the bike.

 

[katanamangler]

Back on topic: here is one of the offending articles. You can see the white mark at the bottom where it was shorting. You can also see the epoxy or paint that has previously applied.

 

[Ian J Hartley]

I don't know whether there is a trend in the failure of these stick coils. Mine failed at around 35K miles, and others have experienced failure around the same mileage.

One of mine was an obvious failure. Disconnect the secondary and the bike stopped. Visually the stick coil looked OK, but when I dismantled it I found lots of corrosion inside, which had compromised the earth. As far as I am aware, these coils are unique in that they have three electrical connections.

1. Pulse from motronic.
2. Earth
3. +ve 12v

After replacing the duff one, the bike ran better, but still not right. So I replaced the second coil as well, and she was back to smooth running. I now have two new coils fitted, and a spare new one for diagnosis in future.

They are overly expensive, but if they don't cure your problem at leaste you will have new coils to use in the future when they do fail.

 

[Packer]

Hopefully that will be problem solved.

 

[katanamangler]

Many thanks for all of the help and feedback, I will update when the new ones are fitted.

 

[Steptoe]

I don't know whether there is a trend in the failure of these stick coils. Mine failed at around 35K miles, and others have experienced failure around the same mileage.

Mileage doesn't matter. I've had bikes in with a failed coil at 6k miles, and bikes with 100K miles and still on the originals.
I've had perfect looking coils fail and coils that look like they've spent their lives at the bottom of the sea and still work perfectly.

But the good news... it seems BMW's latest coil stick offerings (the Mk4 ) aren't failing like the old versions. . Yet.

 

[katanamangler]

Any precautions that can be taken externally to avoid the failure/per-long life or is it in the lap of the God's of mechanical misfortune because they don't seem to be very happy with me at the moment.

 

[Ian J Hartley]

But the good news... it seems BMW's latest coil stick offerings (the Mk4 ) aren't failing like the old versions. . Yet.

Hope your right, the ones I have fitted are made in China by Pulse Electronics, the old version were made in Germany by Beru.

I would gain some small comfort that the Chinese could out manufacture the Germans on Quality and reliability.

 

[katanamangler]

OK 2 new stick coils delivered and fitted today and the bikes runs better but I still feel its a bit rough at the same point, The trouble is I have no direct comparison other than the fact that I assumed that the GS would pull smoothly to the red line but it's not. Any other suggestions to try before I drive it back to the guy who sold it to me and get my cash back. I have 3 older bikes that always need work. I didn't want to buy more work especially at this price.

I'm not in the habit of diagnosing with my wallet but the stick coils were definitely shorting what next? Try and sort it or give it back.

I haven't even had a chance to buy a manual yet.

A secondary question is what would you do if you had paid good money for a GS and it acted up as soon as you got on the motorway. The previous owner is denying all knowledge of the problem and said it was fine. That doesn't explain the paint on the stick coil where it was shorting.