1972 Johnson 4HP Outboard Motor Service Manual, Page 29Get this manual
CLEANING, INSPECTION, AND REPAIR SPARK PLUGS Inspect plugs for cracked porcelain and worn trodesClean the electrodes with point fi1eDO NOT sandblast spark plugsAdjust gap to the specified .030 inchIn re-gapping, adjust only the ground electrode, as attempting to bend the center electrode wi11 crack the insulatorSee Figure 4-7motor performance and premature spark plug result from improper spark plug instalfai1ure lationBefore insta11ing the plug, sure the plug seat in the cylinder head is clean and free from obstructionsSee Figure 4-8Install new spark plug gasket, Screw the plug in hand, then tighten to the specified 17-1 to 20-1 foot pounds1654
Figure 4-8Cleaning Spark Plug Seat
lf threads
stripped in cy1inder head, Heli- coi1 inserts avai1ableCaution should taken when insertsTools and inserts insta11ing Heliavai1able from your parts distributorCLEANING POINTS
After extensive service, the breaker points worn, dirty, out of adjustmentInspect the breaker assemblies for corrosion unusual wearQuestionable breaker points should placedCheck action of the spring and free movement of the breaker Do not change breaker spring tensionDirt, foreign particles, and oi1 very detrimental to contact performanceThe oi1s and acids from person' hand, even though affect contact resistance Oi1 deposits the points wi11 cause them to burn out after very short period of operationNEVER FILE POINTS themremove any traces of dirt from contacts, insert strip of bias tape dipped in alcohol trichlorethylene and work it and down between the pointsRepeat entire cleaning procedure for second set of pointsFigure 4-6Armature Plate dCheck points for good electrical contact, using ignition analyzer as described under "Breaker Point Testing Check and adjust breaker point setting as necessary as described under "Breaker Point Adjustment