Oilhead Tech Pages


Jump Starting or Charging Oilheads with the Battery in Place

Brian Curry  -  bmwbrian@voicenet.com


Jump starting an R11 with the battery in place appears to be almost impossible. The battery is buried under the fuel tank, and the terminals are not available to clip on to. But there is hope. There is a solid connection to the battery positive terminal you can get to without removing the battery.

USE CAUTION HERE AND KNOW WHAT YOU ARE DOING. YOU CAN TOAST THE BIKE AND ELECTRICAL SYSTEM. YOU CAN CAUSE A BATTERY EXPLOSION.

I looked at a R11 closely recently. The is a heavy lead that runs from the battery down to the starter motor solenoid. The starter motor solenoid lives just above the starter motor and is readily accessible. On the left side of the bike, remove the fastener on the rear of the starter motor plastic cover. Pop the plastic cover off. Don't break anything. Now visible are the starter motor, and the solenoid. (The smaller but still decently sized cylindrical thing right on top of it.) The solenoid has two large terminals on it. The lower one goes to the starter motor, the upper, second one has a large red lead on it. This lead goes directly to the battery.

USE CAUTION HERE AND KNOW WHAT YOU ARE DOING. YOU CAN TOAST THE BIKE AND ELECTRICAL SYSTEM.

Use bike size jumper cables with petite (~2-3" clips) not car sized ones. Connect the positive lead from the jumping vehicle to the solenoid terminal that has the large red wire connected to it. Strike the negative lead on an available bolt on the engine or frame. If you get a BIG SPARK check on the connections. It is likely you have reversed polarity and would have toasted all the wiring and electrical stuff if you had clipped it on solid. If you get no spark, or a small spark, clip the negative lead to the engine or frame.

Now try to start the bike. This way the jumping vehicle is supplying lots of juice to the starter motor, the prime consumer when starting, and the bike battery is either charging, or supplying juice to the FI and ABS systems. The starter solenoid terminal can also be used to charge the bike if some reason it cannot be done through the accessory socket.

A caution here: Don't try to put too much current into the battery. Any gases still have to come out the vent tube. Also the battery can get very hot under the tank. And you really can't see what is going on, when you are doing it this way.

Brian Curry


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R-Tech pages maintained by: John Petty for the original author(s) and the Internet BMW Riders
Last Update: 09 September 2010