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Dual Spark 1150 falters under load


John Ranalletta

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John Ranalletta

Well, my new (to me) GS has a problem that neither my '97 RT or my '00 GS ever demonstrated. Under heavy acceleration only or when lugged just a bit, a cylinder drops out or misses.

 

Under normal acceleration, all's fine and cruising at variable speeds doesn't prompt the symptom.

 

Today, for the first time ever, I heard radio frequency interference through the autocom at idle. At first, I ignored it thinking I had a faulty connection in my temporary wiring harness; however, when the acceleration problem exhibits itself, the is RFI and there's no doubt the RFI and the flat spots occur at the same time. I could cause the problem (the miss and accompanying RFI) to occur at will. In fact, it was almost like getting an engine to ping.

 

So, what's up? Sounds to me as if an ignition component is failing under load and at idle!! , e.g. wiring, plug, etc. Which component, when failing, would create RFI?

 

Your opinion is appreciated.

 

BTW, the bike's under warranty, so I'm not worried about getting it fixed.

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The RFI is probably caused by arcing out of the sparks.

I have known spark plugs to fail under load. The resistance of the gap increases at high-pressure, highlighting weakness elsewhere in the system. Inspect the plug's external insulators for signs of tracking.

 

Also, have a look over the bike with the engine running in the dark. Any tracking will show up in the dark.

 

Andy

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Same as Rick said. My 04 1150 was doing the same thing a few years ago on the way to Cody and to Spokane. No dealer seemed to be able to figure out what was wrong. Finally swapped both upper stick coils from a friends bike, fixed mine, now his had the problem. Over on the adventure rider site there have been numerous posts about this problem on 04 1150's. I told them to try the coils, it almost always fixed it.

Marty

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Don_Eilenberger

BMW has the same problem with the same design coils on their cages - they have a blanket replace at no cost warranty on the cars (for 8 years, unlimited miles..) and so far my two bimmers have both gotten a new set of coils.

 

The cost of the car coils is $28 or so each. Wonder how much the bike ones are.. If cheap enough, be worth carrying a spare on the bike on longer trips.

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John Ranalletta

Thanks all...

 

As luck would have it, bike coils are made of unobtanium:

 

01 12127653771 spark plug (BKR7EKC M14) BUY 2 $10.00

02 12121342641 ignition tubing BUY 2 $67.00

02 12121342179 suppressed ignition wire BUY 2 $99.00

03 12122306064 adapter BUY 1 $3.00

04 12131341978 ignition coil BUY 1 $76.00

04 12131342178 ignition coil with interfer.suppression BUY 1 $329.00

05 12132306157 screw BUY 2 $2.00

06 12132306158 plate BUY 2 $1.00

07 07119900510 wave washer (B7) NA 2

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  • 1 month later...
ShovelStrokeEd

Measure the primary resistance of your coil. Should be around 4 ohms or so and then go buy a coil from one of the speed/sport suppliers with the same primary resitance. Coils from a Suzuki or Kawasaki 4 cylinder will work. Do check that the primary resistance is the same. Be sure to retain your noise suppressing ignition wires. Probably no more than 50 or 60 bucks. Coils are simple beasts. You might have to make a small bracket to adapt but it shouldn't be too hard. Dyna Ignition makes all sorts of dual outlet coils and I'm sure you can find one to match.

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Don_Eilenberger
Measure the primary resistance of your coil. Should be around 4 ohms or so and then go buy a coil from one of the speed/sport suppliers with the same primary resitance. Coils from a Suzuki or Kawasaki 4 cylinder will work. Do check that the primary resistance is the same. Be sure to retain your noise suppressing ignition wires. Probably no more than 50 or 60 bucks. Coils are simple beasts. You might have to make a small bracket to adapt but it shouldn't be too hard. Dyna Ignition makes all sorts of dual outlet coils and I'm sure you can find one to match.
It would be nice if there was an aftermarket source for the "stick" coils.. I'm guessing you're not that familiar with the dual-spark oilhead.

 

It uses an "on the plug" coil for the primary plug (centrally located one) - these don't use high-voltage cables since the coil attaches TO the plug, and receive a 12V input pulse.

 

The original dual-output coil (located under the tank) is retained - but used for the secondary plug (the bottom one..) Failure of this coil probably would only result in a bit of surging.

 

On BMW cages the stick-coils are known to fail - and BMW has put in place an extended warranty for them (both of my BMW cages have gotten all new ones once so far..) But it appears Motorad hasn't gotten the message from the home office.

 

If I had one fail - I'd be appealing to BMW since they know it's a problem on the cars - where the coils live in a much more protected environment than the bike engines.

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Before you start changing coils, check the basics. RF interference could be as simple as a cracked spark plug or loose boot at the plug. I had a low rpm misfire under load last year and the boot was half off of one of my secondary spark plugs. Shoved it back on and problem was solved.

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ShovelStrokeEd

I'm guessing you're not that familiar with the dual-spark oilhead.

 

Probably not, only had 74K miles on my 04 GS Adventure when I got rid of it. Changed the plugs on that one a couple of times and no such coil in place on the primary coils. It had two coils up under the tank.

 

Even so, it should be possible to find a place to mount the coil I referenced and run a pair of high tension leads down to the plugs. The wire guards from a single spark should fit.

 

I'm not certain that it wouldn't work as well, or better than the stock setup. I always worried on my 540i about a coil failure. I know lots of modern cars are using them, at least street cars. I also know that the Dyna system I had on my drag bike would fire cleanly with 14.5:1 compression on 1425 ccs and a big load of nitrous with nothing more than a pair of blue coils up there.

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The RFI is probably caused by arcing out of the sparks.

I have known spark plugs to fail under load. The resistance of the gap increases at high-pressure, highlighting weakness elsewhere in the system. Inspect the plug's external insulators for signs of tracking.

Just had two spark plugs replaced on the GS. Doing exactly as you were saying. Don't know if it's the same on the Hexhead.

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Don_Eilenberger
I'm guessing you're not that familiar with the dual-spark oilhead.

 

Probably not, only had 74K miles on my 04 GS Adventure when I got rid of it. Changed the plugs on that one a couple of times and no such coil in place on the primary coils. It had two coils up under the tank.

??? http://www.realoem.com/bmw/showparts.do?...hg=12&fg=05

 

Very odd if it was a dual-spark and didn't use the stick-coil..

 

Even so, it should be possible to find a place to mount the coil I referenced and run a pair of high tension leads down to the plugs. The wire guards from a single spark should fit.

What would you fire the second coil from? One of the feeds for the stick coil? Has anyone done this? I'd be a bit concerned about the current draw of the dual-coil vs one of the stick coils, but mebbe it's just me..

 

Heck, I've seen an oilhead with carbs so I guess most anything CAN be done if you really want to.

I'm not certain that it wouldn't work as well, or better than the stock setup. I always worried on my 540i about a coil failure. I know lots of modern cars are using them, at least street cars.

I agree on the "worry" aspect of it - I'm keeping an eye out for s used good stick coil to toss in the tool kit on the RS to carry along. As long as I have one I'll never need it (Eilenberger's Law of Parts).
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John Ranalletta

Dealer had the bike for 2 weeks and couldn't replicate the problem. Rode it all day today fully loaded and it never missed a beat.

 

Perhaps it was a bad load of fuel, but that doesn't explain the RFI. Oh well, as long as it's running.

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louisvillebob

JPR:

 

Had a similar problem some years ago, faltering under load. I chased that one for months--took apart all kinds of stuff.. Turned out to be something really simple: The plug wire was not firmly seated into the coil terminal. The boot was on the coil tower, but had moved up the wire. The plug wire was close enough to get a spark across the gap most of the time, but under load, the diminished spark couldn't do the job. Pushed the wire up into the proper position in the coil: voila-problem corrected. Simple stuff.

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