The BA1 was an early product for small single cylinder engines that probably appeared before or during the changing of the guards at Bosch USA.Some were branded American Bosch, others as Bosch. It was a rotary wound armature design and quite hot. It probably worked well back in the day when in repair. They suffered from the usual woes of the shuttle wound armature and insulation seepage, lack of lubrication, too much Oregon Rain in the wrong places,fragile potmetal and condenser issues. The key is to handle with care when disassembling as the potmetal ends can be as fragile as eggs, especially when removing the magnet. It may be better to remove the potmetal endcaps before removing the magnet for this reason. Here is some information to keep yours alive and well.
Gap the sparkplug at .025 and all will be well. as always, use non resistor plugs and wires. Polish the interupter contacts shiny and make sure that the rocker pivot pin is smooth and shiny as well, add a small dab of grease to it while you are there. The best way is to remove the screw that anchors the spring, careful that it does not fly across the room and cause discouraging words. At least it is a standard metric thread. The stationary point can be unscrewed or the small brass mount removed , mindfull of the insulators under it. Bad condensers are typical with this one. Many soaked up too much Oregon Rain and developed electrical leakage. A 0.22MFD 400 volt Sprague/SBE/Vishay "Orange Drop" works well here. The 716P 224J is hermetically sealed,mechanically robust and designed to handle spike currents. Use a Dremel MotoTool to remove the top of the defective condenser and remove the innards as shown. Be mindfull of the paper insulator in the base around it as the condenser body is not grounded as it accepts the long hex headed screw that fastens the interupter.
to remove and replace the plugwire can be a challenge. Be carefull when removing the brush and spring, give it a twist clockwise and a quick pull to get it out. Use a well fitting screwdriver to back out the screw. These can be stubborn due to rust and they are standard metric thread. If the head or slot breaks, make a drillbushing that slides into the brushholder and drill out with the tap drill size for 3MMx.5 threads and replace with a pointed stainless steel screw.
The inside is similar to the AB33. the condenser in the base can be a problem. Always check for leakage, then check for capacitance. it should be about .16-.2MFD. Most are found leaky. A leaky condenser(capacitor for Electrical engineering types) will cause pitting at the points and a wimpy spark. Use a modern polypropylene film 0.22MFD 400 volt device as a retrofit. We like the Sprague/Vishay "Orange Drop" polypropylene devices. These are available for many electronics wholesaler as TubesNMore of Tempe, Az. The polypropylene(Mylar) film devices are designed to handle spike currents that may appear when the points open in service.