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Starter Draw on '02 R1150RS

M R Wilson

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Hello all, does anyone know what the starter draw is on my '02 R1150RS is. Voltage drops to 9 volts when cranking. Battery is a year old and I bought it from my dealer. Their battery tester indicates the battery is good but I don't think so. Thanks so much for any information.



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It should not go below 10V while cranking.


Since it's almost winter, open the starter motor and clean and inspect everything in there, especially the magnets!



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First off, welcome to the board :wave:


I agree with Dan, a battery that test good (using a load-tester) should not drop to 9V unless there is a fault somewhere in the system.

Possible causes of this are :

Loose or corroded terminals on the battery leads.

Loose or corroded terminals on the motor to chassis/battery connection.

Worn starter motor brushes.

Stiff up starter motor bearings.

Loose/detached starter motor magnets.


Of that list, the most commonly seen on BMWs are the loose/corroded leads or the detached magnets, although the later starter motors seem to suffer less form that fault.


If it is the starter motor magnets you can buy the can seperately or a new complete motor from Euro MotoElectrics at much lower prices than from your dealer.

Another source of low-cost starters is your local auto-supply store - the same unit is used on small Mitsubushi cars - just take in your old one and see if they can match it.



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Morning Max


Knowing the starter draw won’t tell you much. The only listing I have on the BMW starter is 1100 watts. No mention of starter loading or voltage at that watt draw.


If like similar permanent magnet motorcycle starters I have measured in the 1000cc range (never measured the BMW though) it will run from around 30 amps at warm starter free turning no load to almost 300 amps at cold crank starter stall.


Unfortunately just having the starter amperage draw figure will do you no good unless you can plot it against the starter loading and battery voltage during testing.


On your 9 volt cranking problem? No way to know if you have a simple starter problem, or a resistance in the wiring between the battery and starter, or a starter solenoid issue, or an engine that is turning over with difficulty when cold due to thick engine oil or trans gear oil drag, or something else like a low output battery when cold.


Cleaning the starter out and checking the integrity of the magnets sure never hurts but maybe start with a simple voltage drop test across the battery cables on both the (+) and (-) cables. Then have your battery actually load tested at an independent facility like an auto parts store. (that little hand held battery tester the BMW dealer uses is pretty lame).


Maybe see what the battery cranking voltage drops to on a somewhat warm day start or on a warm engine start. That might shed some light on (IF) thick engine oil or other cold engine drag is part of your low cranking voltage issue. If you crank at 10+ volts on a warm day then look into other things than the starter.


Maybe try jumping from a larger battery to add cold cranking amps to your battery as a test to see if a slightly larger output battery will help your problem.


For what it’s worth most of my BMW boxers have cranked over somewhat slowly if using 20W50 conventional engine oil in real cold weather. I would guess right off that a slow cold cranking would lower the battery available voltage to in the 9 volt range pretty easily.


One more thing to look at: Is your headlight going out during engine cranking? If not suspect the Load Relief Relay not operating properly.


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Thanks for the welcome guys. Thanks for the info D R. I have a real load tester at my shop. I fighting with the local BMW shop about how to test an electrical system other than hooking up as you put it a lame battery tester. They don't know other than what the machine tells them. The voltage was 9 volts after I rode it to the dealer in 50 degree temps. Headlight and accesories off as well. Full synthetic in all sumps and gear cases. With the info you gave me I can take my test equipment and maybe give them a class.

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Hi Max, We can help answer your question, as the guys have above, but what is your actual problem?

Are you actually having trouble starting it.

Are you having trouble with the bike cranking?



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Cranks for a couple of seconds clock resets and then just clicks


Loose connection or junk battery. Test done on your battery could have been faulty. I was always taught The low threshold for cranking voltage was 9.6. You are below it.


1100 watts @ 9.6 volts is 114 amps. I think my R1100RT draws 125 amps on a regular (warm)start.


There are a lot of variables. Once you get below 9.6 volts, things start not working like they should.



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Just heard from the dealer and low and behold the battery is junk. Thanks to all for the tips, information, and advice.






Ps I own The R1150RS '72 R75/5 and a Triumph Daytona 675

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I was having the abs tripping issue when i first got my bike. (not saying that is your problem, but that is a symptom of too much voltage draw on starting.)


When i did my last service, i pulled all of the wires off of the starter including the big cable that goes inside the motor, all of the small ignition wires and all of my battery connections just to make sure they were clean since the bike sat alot. I sanded all of the connection with a bit of 100 grit sand paper but you could use emery cloth or possibly even a stiff small wire brush. after it was all clean and shinny, i havent had a trip of the abs since. Not saying this is the long term fix for the problem, but if you are tripping the abs by 0.5 of a volt, having good clean connections COULD help with this small amount of voltage.

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