If removing the camshaft gear only, follow these instructions.
To avoid damage, do not pry on the timing disk plate. Do not use an impact wrench as that could cause the camshaft to move rearward, resulting in excess camshaft end play.
Remove the three (3) screws securing the timing disk plate to the camshaft gear. Remove the timing disk plate
Install camshaft gear puller to cam gear.
Turn the camshaft gear puller. When the cam gear has moved out approximately 13 mm (1/2 in.) use a pry bar or ratchet to force the camshaft gear to its forward most position. Finish removing camshaft gear. See Figure
If removing the camshaft gear and camshaft as an assembly, remove two camshaft gear thrust plate bolts.
The engine should be mounted in a turnover stand.
Rotate the engine so the front of the engine is facing up (engine in vertical position) for easy removal of the camshaft assembly.
Remove the camshaft from the crankcase by lifting the assembly straight up. See Figure
1. Camshaft Assembly
2. Crankcase Assembly
Avoid damage to the camshaft journals and bushings by removing the camshaft from the crankcase by lifting straight up.
Cleaning and Inspection of Camshaft
Follow these steps to clean and inspect the camshaft.
Wash the camshaft in a suitable solvent using a soft bristle brush.
Visually inspect camshaft. If any lobes are scuffed, scored or cracked, replace camshaft.
Beyond visual inspection, evaluate camshaft journal and lobe condition using a micrometer as follows:
Inspect camshaft journal for wear. Using a micrometer, measure camshaft journal diameter. If journals are worn beyond limits, replace the camshaft.
Check camshaft lobe wear using a micrometer. Measure across (A-D) and across (B-C). Subtract (B-C) from (A-D). This will give cam lobe lift. Replace camshaft when cam lobe wear exceeds specifications.
Visually inspect thrust plate for wear, cracks or distortion. Use a micrometer to measure thrust plate thickness. Replace thrust plate if worn, damaged or if excessive end play is measured.
Visually inspect camshaft drive gear for worn or damaged teeth. Inspect the timing disk plate.
Assembly of Camshaft
Assemble the camshaft, thrust plate, camshaft gear and timing disk plate as follows:
Support the camshaft in an appropriate arbor press.
Place the thrust plate on the keyway end of the camshaft against the bearing journal.
Insert the Woodruff key into the keyway.
Use a thermomelt stick, available at welding supply stores, to determine the temperature.
Press cam gear onto camshaft.
Installation of Camshaft Gear
Use the following steps to install the camshaft gear to the camshaft:
Heating a camshaft gear beyond 177C (350F) will cause it to turn blue. Any camshaft gear that has turned blue cannot be reused.
If only the camshaft gear was removed, perform the following steps:
Heat the camshaft gear in an oven to 149-177C (300-350F).
Use welding gloves to install the heated camshaft gear. Remove cam gear assembly from oven. Ensure the cam gear timing marks are aligned with the upper idler gear and install onto camshaft with timing marks showing. Hold the camshaft gear on camshaft until it tightens as it cools, approximately 30 seconds. See Figure
Check camshaft end play by attaching an indicator dial. (End play should be 0.005 0.013 in.) If there is excessive end play, the camshaft has probably slipped back. Remove the camshaft gear and pull the camshaft forward. Check for end play again. Check timing disk run-out.
Inspection of Camshaft Bushing
Perform the following steps to inspect the four camshaft bushings for wear and proper running clearance.
Using a micrometer, measure camshaft bushing journal diameter at two (2) locations, 90 degrees apart, and record readings.
Using a telescoping gage and micrometer, measure the camshaft bushing I.D. with bushing installed in the crankcase. Record the readings.
Subtract the readings obtained in steps 1a and b, to determine running clearance.
If maximum allowable running clearance is exceeded, refer to Specifications
in Section 1.A. Replace the camshaft bushings using the camshaft bushing remover and installer, J 39537
Removal of Camshaft Bushing
When servicing the camshaft bushings, the crankshaft and main bearing must be removed from the crankcase. Use the following procedure to remove the camshaft bushings:
Use the camshaft bushing service set, J 39537
, to remove the camshaft bushings.
The four camshaft bushings have the same inside diameter, but the outside diameter and widths of each bushing are different, as is the crankcase bore into which each bushing fits, as listed in Table
Bushing Bore Bushing Position
Diameter in Crankcase
63.665 mm (2.5065 in.)
63.627 mm (2.5050 in.)
63.550 mm (2.5020 in.)
63.512 mm (2.5005 in.)
25.4 mm (1.00 in.)
63.627 mm (2.4865 in.)
63.157 mm (2.4850 in.)
63.042 mm (2.4820 in.)
63.004 mm (2.4805 in.)
18.0 mm (0.709 in.)
17.5 mm (0.689 in.)
62.649 mm (2.4665 in.)
62.611 mm (2.4650 in.)
62.534 mm (2.4620 in.)
62.611 mm (2.4605 in.)
18.0 mm (0.709 in.)
17.5 mm (0.689 in.)
62.141 mm (2.4465 in.)
62.103 mm (2.4450 in.)
62.026 mm (2.4420 in.)
61.988 mm (2.4405 in.)
18.7 mm (0.740 in.) 16.7 mm (0.660 in.)
Because of the different size outside diameters of the bushings, order of removal is limited as follows: remove the front and rear bushings first. Then, remove the two intermediate bushings through the front of the crankcase.
Using a camshaft bushing remover and installer tool, J 39537
, select the proper size expanding collet and backup nut and assemble onto the expanding mandrel. With the expanding collet collapsed, install the collet assembly into the camshaft bushing to be removed and tighten the backup nut onto the expanding mandrel until the collet fits the camshaft housing. See Figure
; see Figure
1. Pulling Nut
6. Camshaft Bushing (See Note)
2. Puller Screw
7. Backup Nut
3. Thrust Bearing
8. Expanding Collet
4. Extension Tube
9. Expanding Mandrel
5. Puller Screw Extension
10. Pulling Plate
Camshaft Bushing Removal
1. Rear Bushing
3. Front Intermediate Bushing
2. Rear Intermediate Bushing
4. Front Bushing
Hold the end of the puller screw with a wrench to prevent it from turning when tightening the pulling nut.
Assemble the puller screw and extension, if necessary, and install onto the expanding mandrel. Tighten the pulling nut against the thrust bearing and pulling plate to remove the camshaft bushing.
To remove the rear bushing, install the puller screw from the rear of the crankcase. All other bushings are removed by going through the front of the crankcase.
Installation of Camshaft Bushing
Perform the following steps to install the camshaft bushings: