4. Inspect for axial wear between flyweight and axle using shank of a new No. 35 drill as a gauge. Hold
flyweight so outer radius is in alignment with rim of cam flange and try to insert drill shank between
flange and flyweight as shown in figure 74-14. Do not force drill. If drill can be inserted, replace cam
assembly.
5. Inspect for excess radial wear between flyweight and axle using the 11-10041 flyweight gauge. Insert
gauge between flyweights and against cam hub as shown in figure 74-14. If gauge cannot be inserted
easily, remove burr from edges of hub keyway with a small file. Hold gauge firmly against hub, at the
same time squeezing flyweights against gauge. If inner end of either flyweight heel touches gauge,
replace cam assembly. If parts are near limits, check clearance between flyweight and gauge with a
0.003 inch feeler. If flyweight heel is tight on feeler, replace cam assembly.
—CAUTION—
Never attempt to repair any part of a rejected cam and flyweight
assembly.
6. Inspect ears of coupling body for grooves worn by tail of flyweights and wear at triggering ramp and
cam stop contact areas. (Refer to figure 74-15.) If either ear shows a perceptible groove or a ridge can
be felt when fingernail is drawn across the surface, replace coupling body.
7. Inspect drive lugs of body. If wear is noted, measure difference between worn and unworn areas on
drive lug surface. If difference is in excess of 0.015 of an inch, replace body.
8. With spring released and free, it should form a smooth spiral curve with no sharp bends or flat spots.
(Refer to figure 74-16.) If spring is deformed, replace it.
9. Inspect spring for cracks particularly at ends and around spring eyes. Inspect coils of spring for
excessive wear. If grooves or ridges are worn in coils or cracks are found, replace spring.
10. Inspect housing for cracks, stripped threads, or other damage. Replace if necessary.
INSTALLATION OF IMPULSE COUPLING
1. Check mating cam assembly and body for magnetization which would prevent flyweights from
engaging. Hold assembly as shown in figure 74-17 and push upper flyweight against body. When
released, flyweight must drop down. If flyweight sticks to body, parts are magnetized and coupling
may not function. Perform test on both flyweights.
2. To demagnetize, place body over shaft of a charged rotating magnet and spin body rapidly by hand.
While body is still spinning, invert magnet so body falls off. Catch body in hand and repeat test for
magnetization.
3. Clamp one drive lug of the body in a padded jaw vise with spring recess side up.
4. Orient spring with body for correct rotation. On clockwise couplings, spring must coil in a clockwise
direction from outside toward center when viewed from spring recess side of body. (Refer to figure
74-18.) Insert eye of outer end of spring into hole drilled in inner rim of body.
5. Using heavy gloves to protect the hands, wind spring into body manually, lifting spring coils one at a
time over projections on body. Extreme care should be used to avoid scratching or nicking spring.
After winding spring, brush a coating of light oil over spring coils.
6. Pry up one and one-half turns at inner end of spring with a small screwdriver and support in position
as shown in figure 74-19.
74 - 12 - 00
Page - 74-16
Reissued: August 1, 1986
2J12
PIPER AIRCRAFT
PA-28-236
MAINTENANCE MANUAL
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