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#998261 - 10/03/17 05:13 AM Stickcoils-ectomy - Yes or No?  
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Imgnr Offline
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Imgnr  Offline
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So, I've been getting horrendous fuel mileage on my '04 Rockster (50 miles before the light comes on). Turns out that both top plugs are not firing. I've done lots of research on this site, and others. I ordered new (used) coils and they didn't work. There is a small possibility that all 4 coils in my possession are bad but I don't think that's a high likelihood. I don't have the technical knowledge to do a full electrical diagnosis.

Then I read about the stickcoils-ectomy. I didn't name it. Anyhoo, the person simply connected the bottom plugs to the top ones and called it a day. Went from dual spark to single spark but he says the bike runs like a champ.

Anyone done this? Thoughts?


No sparkenzie BMW but learning...
#998262 - 10/03/17 09:20 AM Re: Stickcoils-ectomy - Yes or No? [Re: Imgnr]  
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roger 04 rt Offline
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roger 04 rt  Offline
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The simple answer is that it will function but it will function as if you retarded the timing several degrees.

The reason is that with two plugs firing, the mixture gets ignited and starts burning at two spots, hence it burns faster and reaches a higher peak pressure in the cylinder. As a result, bmw retarded the ignition timing compared to the single spark. I don’t know but how much, at what RPM/TPS points in the ignition map. You could buy a used single spark Motronic if that concerned you.

The other approach would be to figure out whats wrong with the upper coils. I’m sure you can get plenty of help here. You could start by checking if you have 12v at each stick coil.

#998264 - 10/03/17 10:14 AM Re: Stickcoils-ectomy - Yes or No? [Re: Imgnr]  
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dirtrider Offline
The Oracle
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Originally Posted by Imgnr
So, I've been getting horrendous fuel mileage on my '04 Rockster (50 miles before the light comes on). Turns out that both top plugs are not firing. I've done lots of research on this site, and others. I ordered new (used) coils and they didn't work. There is a small possibility that all 4 coils in my possession are bad but I don't think that's a high likelihood. I don't have the technical knowledge to do a full electrical diagnosis.

Then I read about the stickcoils-ectomy. I didn't name it. Anyhoo, the person simply connected the bottom plugs to the top ones and called it a day. Went from dual spark to single spark but he says the bike runs like a champ.

Anyone done this? Thoughts?


Morning Imgnr

You will be far better off repairing your stick coil problem than trying to make it a single spark engine.

It is a possibility that you have 4 bad stick coils but not that probable.

There is a good chance that your 04 bike has second (load relief) relay powering the upper spark plug coils.

So first thing, do as Roger suggests & check the green/black wires going to the upper coils with the engine running for 12 volts on those green/black wires.

If no 12v to the upper coils then that usually points to a power relay problem, or a power/ground problem TO that second load relief coil. Or a broken wire between the relay & the upper coils.

I have worked on very few Rocksters but 2nd load relief relay is usually in the center row of the fuse box on the L/H end. That relay needs full time battery 12v (no fuse) going to it (red wire) from battery (+) post. Needs full time ground going to it from battery (-) post.

The trigger circuit to that second relay is 12v direct (green wire) from ignition switch but that is the same circuit that runs the lower coil so it is probably working if the engine is now running on the lower spark plugs.

If your 04 is by chance a bike without the second load relief relay (really just a power relay) then the upper coils are powered by the same green wire that powers the lower spark plug single coil so that circuit must be working if the engine runs now, so if no 12v to the upper coils, it is probably just a simple broken wire or bad solder joint.

Pretty easy to at least see if your upper coils have 12v to them with engine running so do that first. If you find NO POWER to the green/black wires to the upper coils then post back & we can help you track the problem to it's root failure point.


[Linked Image]


Last edited by dirtrider; 10/03/17 10:41 AM.

D.R. ___
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#998320 - 10/04/17 03:21 AM Re: Stickcoils-ectomy - Yes or No? [Re: Imgnr]  
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Imgnr Offline
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DR - There is nothing in the space that's labeled "Relay #2". No relay, no receptacle. Does this mean I have an early R1150? I will take my tank off and try tracing the wires and checking that the solder joints are not cracked. Any detailed advice on what to look for would be greatly appreciated.

I couldn't cancel the order for the set of R1100 plugs so I have that handy in case I can't figure it out. Just in case...


No sparkenzie BMW but learning...
#998329 - 10/04/17 11:29 AM Re: Stickcoils-ectomy - Yes or No? [Re: Imgnr]  
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dirtrider Offline
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Ohio
Originally Posted by Imgnr
DR - There is nothing in the space that's labeled "Relay #2". No relay, no receptacle. Does this mean I have an early R1150? I will take my tank off and try tracing the wires and checking that the solder joints are not cracked. Any detailed advice on what to look for would be greatly appreciated.

I couldn't cancel the order for the set of R1100 plugs so I have that handy in case I can't figure it out. Just in case...


Morning Imgnr

I have worked on so few Rocksters that I am working outside of my direct knowledge zone on this.

My book shows both an early 1150 Rockster without a 2nd load relief relay (power relay) & a later 1150 Rockster that uses a 2nd load relief relay. But it doesn't show the changeover date or any other identifying information. (books have been wrong in the past so I really don't know for sure)

In any case you REALLY need to check for 12v power to the green or green/black wires going to the upper coils with the engine running. If you have 12v power there then really no need to trace wires or look for any relays.

If you don't have 12v to the green or green/black wires going to the coils then you will have to troubleshoot the upper stick coil circuit(s).

If you don't have 12v to the green or green/black wires at the upper coils & definitely can't find a relay that powers them then (personally) I wouldn't waste my time tracing wires or checking that circuit but would instead just make a simple power relay system to power the upper coils (that 2nd load relief relay was added for a GOOD reason & would be worth while taking the time to make one for your bike).

Pretty simple circuit--power relay gets 12v B+ from battery + post, gets ground from battery (-) post, gets initiation (pull-in) power from existing lower coil green wire, & power output goes to existing upper coil green or green/black wires.


D.R. ___
Sent from my rotory dial wall phone!
#998337 - 10/04/17 01:26 PM Re: Stickcoils-ectomy - Yes or No? [Re: Imgnr]  
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roger 04 rt Offline
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#998351 - 10/04/17 04:36 PM Re: Stickcoils-ectomy - Yes or No? [Re: Imgnr]  
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Imgnr Offline
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DR - Looks like there are three wires to the stick coils. So the green/black should be +positive. What about the other two?

Roger - I might give this a try. I'm not too comfortable cutting into factory wiring though. Can you please clarify what the two yellow circles are? Do I join all these wires together? What colors are they? Also, where is the connector located?

Thank you!


No sparkenzie BMW but learning...
#998352 - 10/04/17 04:42 PM Re: Stickcoils-ectomy - Yes or No? [Re: Imgnr]  
Joined: Jun 2010
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dirtrider Offline
The Oracle
dirtrider  Offline
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Ohio
Originally Posted by Imgnr
DR - Looks like there are three wires to the stick coils. So the green/black should be +positive. What about the other two?


Afternoon Imgn

Yes, 3 wires.

The green or green/black is 12v power TO the coil.

The brown is coil RFI shield ground

The black/green or black/violet (depends on side) are the coil trigger wires that run back to the Motronic.

Last edited by dirtrider; 10/04/17 04:44 PM.

D.R. ___
Sent from my rotory dial wall phone!
#998408 - 10/05/17 10:03 AM Re: Stickcoils-ectomy - Yes or No? [Re: Imgnr]  
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Alan Sykes Offline
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My personal contact, Helmut, in the Archivists' Department of the BMW Motorrad factory in Berlin Spandau might be able to look out the VIN change for when the factory decided to mod the spark plugs with separate load relays. Mind you we're talking thirteen years back....

I'll chase him up. He owes me a round of beers with Rostbratwürste from 2 years ago anyway.

Simple way to establish the change on our bike is of course to lift the lid on the fuse box under the seat and see if there's that extra relay located to the right of the Pink-coloured coding plug.

AL in s.e. Spain


This is a list of the people I'd trust with my bike
#998411 - 10/05/17 11:05 AM Re: Stickcoils-ectomy - Yes or No? [Re: Imgnr]  
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roger 04 rt Offline
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roger 04 rt  Offline
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Originally Posted by Imgnr
DR - Looks like there are three wires to the stick coils. So the green/black should be +positive. What about the other two?

Roger - I might give this a try. I'm not too comfortable cutting into factory wiring though. Can you please clarify what the two yellow circles are? Do I join all these wires together? What colors are they? Also, where is the connector located?

Thank you!


Imgn, the yellow highlights on the schematic show the added pieces. The highlighted circles are the new bundles, meaning those wires are all connected together when you are done. (To the right of that is a bigger circle which you remove, which connects all the green wires together before you begin.)

So to make this modification work you have to take apart a bundle of 12 green wires and rebundle them into two separate groups. One group has 10 wires, the other new bundle has 4.

If the functions in the schematic don’t make sense, it would be a good idea to get some help.

Last edited by roger 04 rt; 10/05/17 11:12 AM.
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