December 13, 1961
Bulletin No. SB-883
Magneto Ignition Coils
SUBJECT: COIL INSULATORS;
50 h.p. V4(L) & V4S(L) - 10 thru 11B
75 h.p. V4S(L)-12 thru 14B.
Many magneto ignition coils for the subject engines have been returned to the factory
as a result of having burned through the end insulation. Because of the proximity of
the coil's ends to the wall of the magneto housing, the secondary voltage eventually
burns a new path through a relatively thin area of the coil's end insulation, and
discharges to ground via the magneto housing instead of through the spark plugs.
When this occurs, spark plug firing becomes either nonexistent or extremely erratic.
The illustrated coil insulator has been
designed to provide additional insulation
at the ends of the coil, and will prevent
coils breaking down through their end
insulation. To assemble the insulator
on the coil, pass both coil wires through
the rectangular opening in the insulator,
slip them through the slits to the small
holes on each side, and slide the insul-
ator against the end of the coil. One
insulator is required on each end, (2 per
coil).
While these insulators are now being used in currently manufactured 1962 magneto equipped
V-75 engines, the first few models were built without them. To eliminate the possibility
of disabled coils, we recommend installing insulators on these and earlier engines when-
ever they are brought in for service.
The insulator's part number is 510538, and is available from Parts Distributors at the
list unit price of $.05 less the standard parts discount.
JOHNSON MOTORS
W. W. DeWees
Service Department
WWD:jg
NOTE: Post on your V-50 & V-75 indexes.
W. W. DeWees