Harley Davidson Shovelhead Connecting Rod Bushing Reamer

Oversize Ring End Gap
Figure 3-11A. Late Style Compression Ring
Motorcycle Mechanics Institute

Ring gap (space between ends) must also be as specified, see "Specifications," Section 3.

To check ring gap, place a piston in cylinder with top end of piston about 1/2 in. from top of cylinder. Place ring in cylinder bore squarefy against piston and check gap with thickness gauge (see figure 3-12),

Use onfy standard size rings and piston in standard bore, and oniy matching oversize rings and piston in the same oversize bore.

If gap is less than specified, ring ends may butt under expansion, and be scored or broken. Compression ring gap may be increased by filing with fine-cut file.

Use a commercially available piston ring expander (figure 3-13) to guide and slip rings over the piston into their respective grooves without over expanding or twisting rings and damaging the finely finished piston surface

Figure 3-13, Assembling Rings with Ring Expander

See Figure 3-14. Ring gaps should be staggered on either side of the piston pin. Do not place ring gaps at thrust surfaces of piston. Also, gaps on the oil control ring top and bottom rails, shoud be spaced 1" either side ot the oil control expander ring gap.

Oversize Ring End Gap

Figure 3-13, Assembling Rings with Ring Expander


When piston pin bushing is tight in rod but is worn to excessive pin clearance (0.002 in. or more) it is possible to service by reaming oversize and fitting an oversize pin. However, in most cases, it is recommended that a new bushing be installed and reamed to fit a standard pin. The objection to fitting upper end oversize is that considerably more time is required for the job. New pistons, standard or oversize, obtained from factory are supplied correctly fitted with standard pin, and may be installed in a short time if the rod bushing is already reamed to standard size. If bushing has been reamed oversize, either a new bushing must be installed and reamed to standard size or piston must be reamed oversize to fit an oversize pin, which involves extra time.

When replacing bushings in connection with only a top overhaul, use Harley-Davidson special tools as shown in Figure 3-15, Bushing Tool, Part No. 95970-32A and Connecting Rod Clamping Fixture, Part No. 95952-33. Be careful to start new bushing with bushing oil slot in _ ignment with oil slot in rod.

Ream new bushing to size with Special Reamer, Part No. 94800-26. A properly fitted pin should have 0.001 in. clearance; with this clearance, pin will have just noticeable shake in bushing. Fitting tighter is likely to result in a seized pin or bushing loosened in rod. A 0.004 in. oversize pin is available for use with worn bushing. Ream old bushing to correct size for oversize pin.

Figure 3-15. Replacing Rod Bushing


In refitting and reassembling connecting rods, and finally fitting pistons, rods may be bent or twisted, throwing upper bearing and lower bearing out of alignment with each other.

After pistons have been installed, rods must be checked and re-aligned as necessary. If a rod is bent or twisted, piston has a "cocked" relation to cylinder bore and the result is excessive noise and rapid wear.

Check rod alignment with Piston Squaring Plate, Part No. 96179-18, as shown in Figure 3-16. Be sure crankcase face is clean and free from burrs so that squaring plate seats fully.

Figure 3-16. Checking Rod Alignment


Piston skirt is cut away at bottom (below piston pin) for flywheel clearance, therefore, it cannot be used with squaring plate for checking rod alignment. Temporarily install special piston with flat bottom skirt. Part No. 96180-76, to check rod alignment.

If a rod is in perfect alignment piston bottom will rest squarely on plate when flywheels are turned so that crank pin is in forward and rear position. This check, to be accurate, depends upon checking with crank pin alternately in both forward and rear positions. It is the change of roc angle, resulting from changing crank pin from one position to the other that influences the seat of piston on squaring plate and thus indicates whether or not rod is in alignment.

Insert narrow strips of paper of equal thickness underneath piston, one on each side, below piston pin, as shown in Figure 3-16. Press piston down lightly with finger tips resting on center of piston head and pull first one paper, then the other, partially from underneath piston. If piston is perfectly square (rod in alignment), both will have the same amount of drag.

If rod proves to be out of alignment, it can be straightened by means of a bar inserted through piston pin, as shown in Figure 3-17. Use a bar with a diameter as close to the hole diameter in the piston pin as possible. The manner in which piston seats on squaring plate indicates as follows:

1. Piston high on same side, both crank pin positions; rod is bent.

2. Piston high on opposite sdes as crank pin position is changed; rod is twisted.

3. Piston square or nearly square with crank pin in one position and high on one side with crank pin in other position; rod is bent and twisted.

Figure 3-15. Replacing Rod Bushing

Correct as follows:

1. To straighten a bent rod, insert straightening bar through piston pin hofe on low side of piston and apply upward force.

2. To straighten a twisted rod, insert straightening bar through piston pin hole on high side of piston, and if crank pin position is to front apply force to rear - if crank pin position is to rear apply force to front

3. To straighten a rod that is bent and twisted, remove bend first and then remove twist.

Figure 3-17. Straightening Connecting Rod

After rods have been aligned check to see that pistons center in crankcase cylinder opening, without side pressure on upper rod ends. If further realigning is necessary to center pistons, correct by dressing off end of rod bushing on interfering side with a file. This allows the piston to shift slightly on rod to find a more suitable alignment of rod, piston, and cylinder bore.


Attach piston to connecting rod with a piston pin. If the piston is heated in boiling water, the pin may be inserted into piston as a slip fit.

After installing piston pin to connecting rod, install new piston pin took ring using Internal Lock Ring Pliers, Part

Figure 3-18. Slipping Cylinder over Piston

No. 96215-49, The numbered side of the lock ring should face the oulside of the piston.

Make sure ring groove is clean and that ring seats firmly in groove, If it doesn't, discard the ring and install a new one, A lock ring loosely installed will rapidly loosen further in service and finally wilt come out of piston groove, resulting in both piston and cylinder soon being damaged beyond repair. Never install a used lock ring or a new one if it has been installed and then removed for any reason. Always use a new lock ring.

Lubricate cylinder walls, pistons, pins and rod bushings with engine oil. Turn engine unlit crank pin is at bottom center. Install new cylinder base gasket. Position Piston Inserter Ring Tool, Part No. 96333-51A on rear piston and slip rear cylinder down over piston as shown In Figure 3-18.

Install spacers (one side of the spacers is marked "up"). Install nuts and tighten them down evenly. Torque nuis to 32 to 36 ft-lbs. Repeat process to assemble front cylinder.

Assemble cylinder heads and remaining portions of motorcycle as indicated in "Assembling Cylinder Heads." and reverse order of "Stripping Motorcycle for Engine Repair."

Figure 3-17. Straightening Connecting Rod

Figure 3-18. Slipping Cylinder over Piston

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