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R1150RT spark plug reading and electrical problems


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Hi Last fall, I bought a 2003 BMW R1150RT and made 4000 kms before storing it for the winter.


Before my last trip in the last fall, the battery didn't have enough charge to start it so I had to recharge the battery for this last trip, I kept a 300ma charger on the bike for all the winter. Today, it started like a charm but two things didn't work. The clock doesn't hold the correct time and the windshield motor don't work, What could it be ?


I changed the oil today and adjusted the valves, As there was old fall gas in the tank, I went to the service station to fill the tank. The bike has a rough idle and there's some throttle hesitation when crusing and accelerating. It made that a little bit last fall but seems that it is worse this spring. After doing a high speed ride, I looked at the color of the main spark plugs. Left side is light tan brown but the right one is near WHITE !!!. This means ultra lean condition on the right cylinder. At idle. If i open just the left throttle, the bike will rev but if I try it only on the right cylinder, it stalls. Again meaning ultra lean condition on right cylinder. The spark plugs have 5000 kms on them,


I have to synchronize the two sides but what could be the problem with the ultra lean condition on the right side ?




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Afternoon legarem



Both those plugs look about right on today’s lead free gasoline and

fuel air ratio controlled by the 02 sensor. They are all pretty white these days. You need to look closely at the very top of the center porcelain for a very light tan halo and even that can be white with some fuels.



You ask----“ At idle. If i open just the left throttle, the bike will rev but if I try it only on the right cylinder, it stalls. Again meaning ultra lean condition on right cylinder”


Believe it or not that is totally normal also. The left side has the TPS (throttle position sensor on it) so as you open the left side throttle it adds all the fuel it needs (actually more than it needs). But on the right it has NO TPS sensor so when you open that side all you get is air but NO added fuel.


On your rough idle? Get some new fuel in that bike then run it a while to see where you are at. If still a bad idle check the compression and valve adjustment and if all OK there maybe look into the 02 sensor as maybe acting up (maybe try riding with it disconnected) .


Added: if your bike has lower (secondary spark plugs) are those both clean without oil fouling.


If you do have a twin spark engine see if the engine will run with the lower plugs shorted (don’t just pull the wires off as that can ruin a coil). Maybe you have an upper (stick coil) acting up.



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Lower spark plugs are the same color as the main ones. I changed the coils from l to r and the same cylinder has spark plugs paler than the other one,



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I have become a believer in 'Sea Foam"----purchased at your auto parts store. Though a skeptic at first, I used it on the recommendation of a trusted friend and after seeing some good forum reports on it. It is reputed to clean a carb or throttle body and I've been impressed with the results of using it on my BMW and my dirt bike. Doesn't cost all that much and it's worth a shot to see if it will help with your problems.

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Lower spark plugs are the same color as the main ones. I changed the coils from l to r and the same cylinder has spark plugs paler than the other one,


Morning legarem


See if it will run and idle on JUST the upper plugs. Just swapping coil sides doesn’t tell the whole story as it can run on the bottom plugs with one of the uppers not working correctly. Spark plug color doesn’t necessarily tell you if it is sparking or not as what you are viewing is combustion completeness not spark as long as something triggers the cylinder combustion.


If you are really worried about it being lean on one side just swap the fuel injectors side to side and repeat your runs. On your bike BOTH injectors are powered and triggered from the same circuits so electrically what one does so does the other. So that leaves the only difference as the injectors themselves.


I presume you have the idle AND above idle side to side TB vacuum balance set within reason?


What does the compression show side to side?


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Last fall, the battery went weak. As mentionned, during all the winter, there was a 300 ma charger permanently conected to the battery. During this weekend the bike started like a charm without any hesitation. As this is the original 2003 battery, it is probably reaching it's end but now it is doing his job.


The clock problem began last fall when the bike was hard to start. the windshield motor worked last fall but don't work now.


As I kept the bike without his shell, I'll probably buy a Yuasa battery this week but will do discharge test on the old battery to be sure.

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As yesterday was the first time I've done mechanics on this bike. (I bought the bike last september and it stayed unused during winter)) The throttle bodys are not now synchronized. I have to buy manoneters or other kind of synchronization vacuum tool to do the job. I would prefer something not too costly I can also use with other bikes than BMW twins.


After doing synchronization, I'll look if everything is ok




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Morning again legarem


You can make a very simple and VERY effective homemade “U” tube manometer from a piece of clear PVC hose about 5/16” or 3/8” id. In fact that homemade “U” tube is actually more accurate than most of the high dollar syncing tools as your homemade manometer reads in inches of water not inches of mercury and they do read the cross side delta not to atmospheric pressure.


I’m on the road right now so don’t access to my shop pictures, maybe someone will be kind enough to post a picture of a simple homemade U tube manometer.


You really need to get the balance set—both at idle and at about 2000-3000 RPM’s.


Edit: spelling corrections (I hope) -- one hand typing while driving doesn’t allow proper proof reading.

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Battery being weak "Zeros" the clock on startup. In spite of the bike starting easily, your battery is very likely on its way out.


Dirt rider is on the right track. If you have a problem mechanically, it is likely a bad primary spark coil. If neither has been replaced, and you need one, I would consider buying 2. The replacements are better, from what I hear.


The windshield checklist would include the fuse, (Under the seat, cover over the box), the relays, same place, and the switch, or the wiring to it. Good Luck.

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Do you know anyone else with a twin spark BMW?

If so, once you have done the checks suggested all above, I would heartily recommend swapping your stick coils with someone else to see if that improves things. The coils can still operate - but badly, giving rough running. Frustratingly they can still show a spark when you hang a plug in there to check.


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Tonight, I cleaned the brass air adjustments and the throttle body holes and the idle is now at 1100 rpm and not erratic like it was.


I checked the price for the stick coils today. Is seems that the 12 13 7 680 644 is again replaced by another number which is: 12 13 7 715 853. The price is now 125.51. Ouch !!!


The BMW stick coils for their cars is near $30, Why they stole motorcycle peoples like this ?


I've done some tests tonight. I unplugged the wires that goes to the stick coils and it didn't change a lot the idle speed when doing 1 cylinder,


I tried it with lower spark plug caps (placed a spark plug touching the metal in the cap) and the idle lowers a bit but the engine didn't stall.


It seems that the lower spark plugs are doing more job than the others.



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I have an 02 RT, removed battery in Nov. had it tested, and took it home. Put battery in, and same results as you. Started like a charm, clock will not hold time and my windshield will not function. The battery place that I deal with....just do battery, nothing else, they said that they would love to sell me a new one, but I simply didn't need one. I have a Gel battery.

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That's really weird. If the battery can easily start the bike why is there clock and windshield problems like we have. You're the third person I heard about the same problems. There's a solution elsewhere to understand why,


About throttle body synchronization. I looked at youtube about the U tube manometer and I'll go with that, That's cheap, easy to do and will give precise results. Thanks

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Morning legarem


I wouldn’t worry too much about the battery at this point. While a low or failing battery can cause the clock to re-set at engine starting (the clock’s keep alive power supply gets pulled too low for the clock to retain memory) “it” (a low or bad battery) should have no effect on the power windshield operation or the engine management system once the engine is running as long as the alternator is working properly.


If you are worried about it just put a voltmeter across the battery once the engine is running. I’ll bet you have plenty of voltage in the system with the engine running. Then try to operate the power windshield, as long as the voltage a stays above 11 volts the windshield should work OK.


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Also, don't consider buying a new stick coil until you have swapped it with a known servicable item. As you have found, it is a lot of money if you don't need it.

BUT, they are very hard to diagnose, as they keep working at a very reduced level. Once you have swapped it, you will probably notice immediately the overall improvement.


Fill out your profile a bit, and maybe one of us could help you with a swap.

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I'v done a U tube manometer and tried it tonight. As seen on you tube, II thought it would be easy to do the adjustments.


i used windshield washer in the manometer because it can be easily seen in the tubes.


I let the motor get warm and plugged the Utube on both throttle bodys. When I started the bike. The liquid was eaten by vacuum. I put again liquid in the U tube but pinched the tubes at starting. It worked but it was hard to read in the tubes because the liquid moved like it was boiling. When I stopped the bike, the liquid was eated again by the vacuum..


I looked at 3000 RPM and it also have to be adjusted.


I went doing a ride and the bike has only a really slight hesitation, Good move but I have to finish the job at 3000 RPM


Some questions


1- Should I use automatic transmission fluid for liquid in the manometer so it will be easier to read (without being displaced like boiling water)


2- Should I have to pinch the tubes when starting and stopping the bike so the liquid will not be eaten by the vacuum ?


Thanks a lot







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I realized that the look alike boiling water was probably because the U Tube was fixed on the bike.


So now why the bike is suckering the liquid at startup and when turning it off ?

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Morning legarem


A properly made and properly hooked up “U” tube manometer shouldn’t allow the fluid to be sucked out on engine start or stop (IF) the TB balance is close to where it should be and there are no vacuum leaks.


So lets start with the U tube itself—ALL vacuum hose connections need to be leak free (absolutely leak free). If one side has a small vacuum leak the other side will show high and suck the fluid out. Using windshield washer fluid is probably too thin bodied to start with. It should work but that type of fluid has such little viscosity that it won’t stick to the tube walls so will want to dance around like crazy. Using 2 cycle oil or ATF would be a good thing to start with. You can always switch to a lighter bodied fluid once you get the TB’s close.


Now on it sucking the fluid out?-- That means that the side the fluid is getting sucked to has higher vacuum then the other side. If the TB’s are adjusted correctly both at idle and off (above) idle it shouldn’t be moving the fluid more than a couple of inches on start, stop, or throttle up/down.


SO, lets start with the basics. -- first make sure BOTH side TB’s are firmly hitting their closed stops and your throttle cables at the TB’s have a little slack in them. If not fix that area first. Then with one hand open and close the twist grip as you feel for one side then the other TB cam hitting the full open throttle stops at the exact same time. If not try to adjust the cable so they are as close as possible.


Next, look closely for any points of vacuum leaks in the TB rubber boots (between TB and cyl head), look for loose clamps, look for splits or cracks, etc.


Things like spark plugs or coil function don’t effect the vacuum enough to make a difference so don’t mess with that (yet).


OK, after the above just hook your manometer up then use a pair of needle nose pliers, or a clamp, or just kink a hose going between the manometer and engine (an aquarium bubbler valve also works great in one side). Anything to completely block one side hose from passing vacuum will work. Then block that one side hose and start the engine. Allow it to idle for a few seconds to straighten out then S-L-O-W-L-Y release the hose blockage a little and see what the fluid does. If it stays in the manometer great. If it goes to one side that means that side has higher vacuum than the other so either open the BBS screw a little on the high side of close the BBS a little on the low side UNTIL the fluid will stay in the manometer with the hose blockage full released. Once it (the fluid) will stay do your fine cross side idle adjustment. Then run the engine up to about 2000 RPM’s slowly and watch the fluid column if the fluid starts to go one way that again is high vacuum side so either tighten that side cable s little to lower the vacuum on that side or slacken the cable on the other side. The thing to keep in mind here is: you are working with negative pressure (vacuum) so the more air you “LET IN” the lower the negative pressure (vacuum) on that side.







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Thanks Dirtrider


The U tube worked correctly if I block one tube when starting the motor and when I turned off the motor. When the motor is working, it doesn't suck liquid and I've done adjustment with good results when riding the bike.


First, i'll check the cable slack and then I'll use an aquarium valve or a clip and ATF liquid. After I will adjust it at 3000 rpm.


Thanks again



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With ATF fluid, the U Tube is a marvelous tool.


Now I have to look at the coils. It really seems that one of the stick coils is bad. As there a new BMW part, (now $125 ea) I have to change both. What peoples call surging problem or hesitation between 3000-5000 RPM seems more related to the coils than valve adjustment and throttle balance. BMW has or had the same problem with their cars. Bremi coils as I have are more prone to this problem.


I'm seriously tempted to use (fit) outboard coils with spark plug cap and wires to get rid of this problem forever. I would have to find long spark plug caps that could fit in the head


If someone tried that, your idea is welcome

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Morning legarem


You have to be very careful if you try to use (2) external coils in that the combined resistance isn’t so low as to burn out the driver (transistor) in the fueling computer. Remember both side coils spark together so the computer will see total current load at each firing.


Probably the safest way would be to find a BMW 1100/1150 pre (twin spark) coil & plug wires then find a place to mount that. The 1100/1150 plug wires should already have long plug boots and the proper wire resistance to protect you fueling computer.


That seems like a lot of work. The new style stick coils seem to be much more robust with very few re-failures.




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I will order the new BMW stick coils today and will redo a TB synchronization with the new coils. As is, the synchronization is unstable. When I rev the bike the two levels in the U tube doesn't return at the same level. I adjusted the BBS again and it is hard to get the same level. The idle is also erratic so I figure that all should be correct when there will be new coils,

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Banging my head against the wall trying to remember were I read someone

posted a alternative stick coil, not bmw. I think they stated matching all the specs of the oem but half the price. Some auto parts store was mentioned, I usually right this stuff down, damn............bang-bang-bang

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Afternoon legarem


The coil(s) by themselves shouldn’t effect the TB balance. The balancing of the TB’s is just the vacuum delta between sides or to atmosphere and that is in relation to a direct pressure drop across the throttle plates nothing more nothing less.


Now if you have a coil acting up enough to cause a cylinder to try and fire on an open intake valve that will cause a big disruption in that cylinder’s vacuum.


A real erratic idle could also effect the cross side vacuum as the RPM might vary enough to cause uneven air flow. Have you removed the BBS screws and used catalytic converter safe carb. clean to clean the BBS screw tips and BBS screw seats/passages in the TB’s? If not do that to see if that will improve the dropped throttle idle. Usually a dropped throttle TB un-balance problem is due to either coked up BBS screws or passages, or coked up throttle bores around the throttle plates, or worn throttle shafts in the TB’s, or wear in the TB at the shaft area.


Have you tried shorting both lower spark plugs and seeing if it will run and idle on only the upper coils? If not try that as it will show if the upper coils are operational. Maybe not under road load but at least at idle.




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I tried to run the motor by shorting the lower spark plugs. It was hard to start, motor was sputtering and finally died. When the lower spark plugs are connected, I disconnect the left stick coil and idle lowered a bit, I've done it on the right side and it didn't affect at all the idle. Inverting the stick coils made the same thing but the lowered idle was according to the other side.


The BBS were cleaned and I used Q tips to clean the TB holes with carb cleaner. They were really dirty. I blowed compressed air in the holes before replacing the BBS.


I'll ride the bike as is until I get my new coils.


Thanks a lot Dirtrider for your help.

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---- When the lower spark plugs are connected, I disconnect the left stick coil and idle lowered a bit, I've done it on the right side and it didn't affect at all the idle. Inverting the stick coils made the same thing but the lowered idle was according to the other side.


Afternoon legarem


Well that does sound like you have at least one bad stick coil.


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If you ever find it, many peoples will be happy to hear about that.


At $125 each, it is hard on the wallet. I still ask the question: Why manufacturers are abusing motorcyclists like this ? For a car, it's under $50.

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The Battery was changed today, The clock is now ok. The windshield motor is connected with the same circuit as the outlet plugs. I made a short this fall with the outlet so the fuse was burnt. Stick coils are coming so I hope that this will be the end of all these problems. As Dirtrider was writing, I'm still unsure about why is there some instability of TB synchronization if the coil doesn't have anything to do with that instability. My bike has only 40 000 miles.

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I found a couple of vacuum reducers on the rack @ Pep Boys that effectively reduce the vacuum "pull". It reduces the interior dimension of your manometer tube. I use one on each end of the tube. Then I just use plain water with a little food color. Very manageable, easy to read and therefore adjust.


These reducers are in the section where they have all the tubing connector tees. In a blister pack.



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Stick coils are coming .


Are you buying 2 stick coils?

if so, why?



The new coils I'll buy are not the same as the original ones I have on the bike. They're 'supposed' to last. I want to get the same part on both cylinders. . Mine are Bremo coils and they reknowned to have a high failure rate even in BMW cars so the good one will eventually fail.


Next time, If I still have again this problem, I will use outboard coils or try to find a car coil substitutes.



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