Chapter 5. REPAIR OF ENGINE (Model RMP-J/1-1OG)

TM 5-4110-217-14

CHAPTER 5

REPAIR OF ENGINE (Model RMP-J/1-1OG)

Section I. ENGINE ACCESSORIES

flat head screws (19) and terminal stud and washers (20)

5-1. General.

holding coil assembly (21) to. frame (22).

This section contains instructions for maintenance

c. Brush and Spring Repairs (fig. 5-2).

of those items which are considered accessories to the

(1) When brushes are worn more than 0.3 inch,

engine.

replace them. Check to see that the brushes move

smoothly in the brush holder.

5-2. Starter.

(2) Measure brush spring tension with a tension

The starter is a 12 volt, 2 brush, direct-cranking

meter (fig. 5-3). Push the brush into its holder and take

type starter. The starter converts the electrical energy of

the reading just as the brush slightly projects from the

the battery into the mechanical energy necessary to

brush holder. On a new brush, the spring tension should

rotate the engine crankshaft until the engine can operate

be 29 to 39 ounces

on its own.

d. Armature Testing.

(1) Testing for grounds. Test the armature for

NOTE

grounds by touching the armature shaft or core and the

The starter Bendix assembly has a detent

end of each commutator bar with a pair of ohmmeter

on the Helix which keeps the pinion gear in

leads (fig. 5-4). If the ohmmeter reading is low, It

mesh with the flywheel ring gear until the

indicates a grounded armature. Replace armature.

engine starts and runs. Centrifugal force

(2) Testing for open circuit.

The most

retracts the pinion on the Helix Once

commonplace for an open circuit to occur is at the

engaged the pinion remains in mesh with

commutator riser bars. Inspect the points where the

the flysheel ring gear until the engine is

conductors are joined to the commutator bars for loose

running.

connections.

a. Removal. Refer to paragraph 3-41 and remove

(3) Testing commutator runout. Place the

the starter.

commutator in a test bench and check out runout with a

b. Disassembly (fig. 5-1).

dial indicator (fig. 5-5). When commutator runout

(1) Remove band cover (1) by loosening its

exceeds 0.004 inch, reface the commutator.

clamping screw.

(4) Testing armature shaft runout.

The

(2) Remove four screws (2) and washers (3) to

armature shaft as well as the commutator may be

partially detach head assembly (4). Release brushes (7)

checked. A bent armature can often be straightened, but

from brush springs (5) to fully detach head assembly (4)

if the shaft is worn, a new armature is required.

(3) Brush springs (5), strap (6) and brushes (7) can be

(5) Testing field coils for grounds. Place one

removed if replacement is required.

test lamp prod on the connector and the other on a clean

(4) Remove armature thrust washer (8) from

spot on the frame after unsoldering shunt field coil wire.

shaft.

If the lamp lights, the fields are grounded either at the

(5) Remove two screws (9) and lockwashers

connector or In the windings (fig. 5-6).

(10) to release pinion housing (11). Remove drive end

(6) Testing field coils for open circuit. Place

bearing (12), if required.

one prod on the connector and the other on a clean spot

(6) Loosen setscrew (13) to slide off drive

on the brushholder (fig. 5-7). If the test lamp lights, the

assembly (14) from armature shaft. Remove key (17).

field coil is okay. Check all brushholders in the same

manner.

CAUTION

e. Drive Assembly. Check for damage of the

Care must be taken not to thread-out the

pinion gear. Verify that the drive shaft is free of rust,

worm gear on the drive assembly. It is

burrs or bends so the screw shaft can move freely along

difficult to rethread. Keep it in a fully closed

it.

A damaged pinion or screw shaft requires

position unless further maintenance is

replacement of the drive assembly.

required on the drive assembly.

f. Cleaning and Lubrication.

(7) Slide off Intermediate bearing assembly

(1) Clean all parts carefully with a dry cloth and

(15) and washer (16) from armature shaft. Remove four

compressed air if available.

Change 3 5-1