Pre-1970 BMW motorcycles: antique, vintage and classic
How to replace a coil when you're stopped on the side of the road

by Craig Vechorik

I always advise riders of vintage BMW motorcycles not to ride anywhere without taking along extra spark plugs, points, condenser and coil. Besides the points closing (corroding) or the plugs fouling, the only other ignition components that cause the bike to stop running is condenser failure and coil failure. The condenser is not a problem to obtain, since a V8 ford condenser can be used, and they are readily available from any auto parts store. The coil is another matter. They are not readily available. There have been several different aftermarket coils available over the years, but their reliability has varied from terrible to pretty good. We at Bench Mark Works LLC have finally come up with a coil that is more dependable. Nothing man-made is perfect, so I still advise you to never leave home without a spare coil.

If you experience hard starting problems when the engine is hot, that is a sign of coil failure. When this happens to you, remove the front cover immediately, to expose the coil to cool air. Try starting it again after ten minutes or so. If it fires up, don't put the cover back on, but ride the bike to your destination. Start shopping for a new coil. If you will carry a spare coil and acquire a few simple tools to add to the tool kit, you can swap the coil out easily on the side of the road.

The tools you will need:
1. one off-set screwdriver
2. two 7/32 open-end ignition wrenches
3. one small straight-blade screwdriver.

1. Begin by removing the front cover from the engine.
Place the front cover under the front of the engine to catch any of the parts that you might drop during this work. The cover will act as a good catch tray, and keep you from losing tiny parts in the grass or gravel on the side of the road.

2. Use a small, straight-blade screwdriver and remove the two spark plug wires from each of the spark plug terminals of the dead coil.

3. Remove the kill wire from the upper left back corner of the coil.

4. The wire from the coil that is attached to the points must be removed next. Use the two 7/32 wrenches to loosen the tiny nut from the bolt on the point base. Remove the nut and remove the lead from the coil, but leave the wire from the condenser attached to the bolt. Temporarily replace the tiny nut and washer, so you do not loose them.

5. Use the offset screwdriver and loosen (but do not remove) each of the slotted screws that retain the clamps that hold the coil to the body of the magneto. Swivel them 90 degrees out of the way and simply lift the coil off the body of the magneto. Replace the dead coil with the new unit, making sure that you have routed the wire on the coil that attaches to the points in a manner that it will not be rubbed or pinched.

6. Swivel each of the hold down clamps back over the center bar of the coil and re-tighten the slotted screws with the offset screwdriver.

7. Remove the tiny nut and washer from the bolt of the points and place the spade lug of the coil wire over the bolt. Replace the washer and nut and tighten them with the two 7/32 wrenches. Take care to insure that the lugs on the end of the coil wire and condenser wire do not contact the base of the points. Both lugs must be insulated from the base, but be in contact with the tiny nut and bolt of the points.

8. Re-attach both of the spark plug leads, and tighten the slotted set screws using the small straight blade screwdriver.

9. Re-attach the kill wire to the upper left back terminal of the coil and tighten the set screw with the same screwdriver.

10 Replace the front cover and continue your journey.

PS If you're stranded without a coil, perhaps we at Bench Mark Works LLC can help. Always carry our telephone number with you. Check our hours of operation so that we may assist you. If you have an emergency, I'll be glad to talk with you or your mechanic, no matter what time of the business day.

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