The Bosch Magneto
The Bosch Magneto
The only care required by the magneto is the oiling of the bearings and the occasional cleaning or adjusting of the contact points. Readjusting the points is necessary only about once every 5000 or 6000 miles.
How to Oil the Magneto
A place for oiling will be found on both ends of the magneto, and four or five drops of oil every 500 miles is sufficient for all needs.
The interrupter lever located inside the interrupter housing is intended to operate without lubrication, and great care should be exercised to prevent the entrance of oil at this point, because if oil gets on the contact points it will prevent a good contact and cause sparking and burning as well as missing.
To Clean Contact Points
If the contact points in the interrupter housing become badly roughened, pitted, or burned after extended service, they should be smoothed with No. 00 sandpaper.
It is necessary to remove the chain guard to gain access to the contact points. After removing the chain guard, take off the interrupter housing cover "8" by sliding off the flat spring "4;" then remove the interrupter housing by working it back and forth. The interrupter lever "2" is removed by sliding off the retaining spring "10" after removing the small screw clamping the tension spring.
Adjustment of the Contact Points
After 5000 or 6000 miles of running the contact points on the magneto may require adjustment. However, if the motor is firing regularly, it is advisable to leave the magneto alone.
A Bosch magneto wrench will be found in the tool kit of all machines with which the Bosch magneto is furnished. The contact points may be set closer by loosening the nut "7" (illustration 18) and then turning the hexagon headed adjusting screw "6" until the distance "5" between the points "3" and "6" is just enough to permit the steel feeler gauge attached to the Bosch magneto wrench to be inserted. This separation is about 1/50 inch. This adjustment must be made when the arm "2" is on the center of the interrupter cam "1" or "9." It may be necessary to crank the motor to get the arm in the correct position for making the adjustment. After the points are the proper distance apart, carefully tighten the nut "7."
Tight Interrupter Housing
Now and then a rider may find that the interrupter housing gets tight. This is generally due to extensive travel through heavy dust or mud. The trouble can be remedied by thoroughly cleaning the housing with gasoline, and then applying a drop of oil.
Testing a Magneto for Trouble
If magneto trouble is suspected, turn the left grip all the way to the right, thereby fully advancing the spark; then disconnect the cable from the spark plug and support its terminal Y8 inch from the metal of the engine, and work the starter pedal briskly. If sparks do not appear, examine the interrupter to see that the contact points at "3" and "6" are clean and that the interrupter lever "2" moves freely.
Due to climatic conditions, the interrupter lever may stick or work stiffly. This can be remedied by removing the lever and polishing the steel pin and fibre bushing to make the lever work properly again. When polishing this stud, polish it only as much as is necessary, because the lever may not be loose enough to shake in the bushing.