Pre-1970 BMW motorcycles: antique, vintage and classic
by Craig Vechorik
How to replace a coil when you're stopped on the side of the road
A WORD OF WARNING - AND SOME STRAIGHT TALK:
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
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 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
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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