Damaged Left Rocker Cover in Accident, Weird throttle position power loss

[chrisinsc]

So, I was hit by an irate female SUV driver and knocked down at low speed hard on the left side. Broke my ankle which got trapped between the silencer and the pavement and the left rocker cover hit so hard it ripped the BMW protector off and it drips a little tiny bit if oil. I checked the plug and it initially seemed to be operating properly but now its not.

Its rougher running after starting normally but at a half throttle while riding its like one cylinder drops out and it bogs down. Maybe the TPS was damaged and has a section which no longer works?

 

[r0ckrat]

Sounds like it might have damaged the plug wire and is only firing on the secondary plug, which wouldn't be able to provide complete burn at higher RPM.

 

[lee]

I checked the plug and it initially seemed to be operating properly but now its not.

What about the coil?

 

[pauls1150]

Might also be worthwhile to pull the valve cover and make sure everything is still aligned...

 

[chrisinsc]

Thanks, guess I will take it apart a little and check on things. The cutout happens at a throttle opening and is not revs related. So rolling at 3K rpm and twist the throttle on to like 3/4 the bike accelerates as I roll the throttle on when its open to 3/4 the cutout happens.

 

[GTRider]

I’d trace the throttle cables, handlebar to actuator and actuator to TB. One may have become unseated or hung up in the fall.

Best,
DeVern

 

[chrisinsc]

Finally got to the bike today. Somehow the tabs on the upper coil broke off so only one spark on the the left/impact side. The impact also bent the two forward bolts that hold the valve cover on. It needs a new cover anyway so new bolts and gaskets will be fitted anyway.

What I am wondering is if the bike is meant to be dual spark until a specific throttle opening and then it switches to the upper plug only until heavy acceleration is done. Then it goes back to dual spark when steady/low throttle openings are being used. That would explain what feels like one cylinder was dropping at the big throttle opening.

Thanks for the ideas folks.

Should I replace both coils at the same time?

 

[pauls1150]

1) I strongly doubt (but don't "Know") that the computer switches the spark back and forth. First because it doesn't on my oilhead, and second, using the lower plug only Would Be less efficient than using the center plug only.
2) Unless you Know it's damaged, why change the "2nd" coil...? If the spark plug looks much darker, it's possible the coil was/is failing; keep in mind that the "perimeter" plug WILL be a little darker under normal conditions just because it's not in as hot an area as the central plug.

 

[chrisinsc]

1) I strongly doubt (but don't "Know") that the computer switches the spark back and forth. First because it doesn't on my oilhead, and second, using the lower plug only Would Be less efficient than using the center plug only.
2) Unless you Know it's damaged, why change the "2nd" coil...? If the spark plug looks much darker, it's possible the coil was/is failing; keep in mind that the "perimeter" plug WILL be a little darker under normal conditions just because it's not in as hot an area as the central plug.

I meant left and right like like. Just the uppers. Also, I had the plugs mixed up before I edited my post. Sorry. I think it runs dual and then drops the lower. All just carport theories from me for sure.

 

[pauls1150]

Speaking from "older oilhead" experience; I'm not experienced with hex- or cam-heads:
If it's anything like our other recent boxers (don't know which specific model you have), then you have two triggers - magnetic pickups - on the front end of the crank, inside the first front cover. One trigger is for the ignition system, and the other is for the fuel injection system.
The ignition section of the computer controls the "when" of the spark (based on additional factors besides where the crank is), but I have never heard of it actually turning either plug off. While the newer computers may (?) independently control the sparks' timing - which would be beneficial when one considers the different requirements of igniting fuel at 1100 rpm vs. 5000 rpm - the peripheral plug will typically show up as a bit darker.
If a coil on the center plug fails (or is about to), starting is a bit more difficult and idle is a bit harder to maintain; fuel mileage will decrease. Das faktory has revised the coils a few times, attempting to improve their reliability (it's happened with their cars too). If a peripheral coil fails, the bike will still start and run decently; you "may" notice a small loss in the throttle response.

 

[AntonLargiader]

The early Hexheads retarded the timing of the lower plugs drastically as the RPM rose, basically making the bike run on one plug. I had almost the exact same scenario as you, and the bike idled OK but became a thumper at mid-RPM. New plugs fixed it for me, but a bad coil would have the same effect.

 

[pauls1150]

Not that it matters, but... I don't understand that: I'd think that as RPM rose, the timing should advance; on the other hand, retarding it would increase overall "combined spark duration", which might also increase efficiency. Heat would increase either way. Hmmm, interesting.... Thanks for the info!

 

[AntonLargiader]

Yes for normal spark advance. I'm talking specifically about the one plug essentially dropping out of usefulness by retarding so much tha tthe engine was relying on the other plug. That's how it was explained to me and it matches my observations.