Valve tappets and guides


The tappet assembly consists of tappet, roller and hydraulic unit. The tappet and roller, under compression force from valve spring, follow the surface of the revolving cam. The linear motion produced is transmitted to the valve stem by the hydraulic unit, push rod and rocker arm. The hydraulic unit contains a piston or plunger and cylinder plus a ball check valve which allow the unit to pump itself full of engine oil to take up all play in the entire valve train.

When hydraulic units are functioning properly the assembly operates with no tappet clearance. The units automatically compensate for heat expansion to maintain a no-clearance condition.

It is normal for tappets to click when engine is started after standing for some time. Hydraulic units have a definite "leak down" rate which permits the oil in the hydraulic unit cylinder to escape. This is necessary to allow units to compensate for various expansion conditions of parts and still maintain no-clearance operation. Push rod assemblies are functioning

1. Oil pressure switch

2. Cover stud nut and washer (4)

3. Oil pump cover

4. Cover gasket

5. Lock ring

6. Scavenger pump drive gear

7. Gear key

8. Scavenger pump idler gear

9. Oil pump body mounting stud 17. By-pass valve nuts and washers (2)

Motorcycle Tappet

10. Oil pump body

11. Oil pump gear drive shaft

12. Feed pump drive gear

13. Feed pump gear key

14. Feed pump idler gear

15. By-pass valve plug

18. Check valve spring cover screw

19. Check valve spring

20. Check valve ball

21. Chain oiler adjusting screw lock nut

22. Chain oiler adjusting screw

23. Chain oiler adjusting screw washer

16. By-pass valve spring Figure following name of part indicates quantity necessary for one complete assembly.

Figure 3D-1. Oil Pump - Exploded View properly if they become quiet before or as engine reaches full operating temperature.


If engine cylinder head is not disassembled, remove push rod cover spring cap retainer. Lift push rod covers and retract push rod adjusting screw until push rod may be lifted out of ball sockets.

Turn out tappet guide screws (1). Lift out hydraulic units (2). Loosen tappet guides by tapping gently with rawhide or soft metal hammer. Insert thumb and forefinger into push rod openings in tappet guide and press tops of tappets against sides of guides.

Remove tappet and guide assembly. Be careful to avoid dropping a tappet through guide mounting hole and into gearcase. Slip push rod cover cork washers (3) out of top of tappet guide (4). Pull tappet and roller (5) out bottom of tappet guide and remove tappet guide gasket (6).


Wash all parts except hydraulic units and gaskets in grease solvent. Hydraulic unit parts are selectively fitted and may not be interchanged so they must be individually and separately washed. Twist and pull hydraulic piston and spring from cylinder and wash parts.

Blow out oil passages in tappets, tappet guides and hydraulic units with compressed air. Insert a length of wire into oil channel openings in tappet guide to make sure passages are open. Air dry all parts.

Examine cams through tappet guide holes in gear-case for nicked, grooved or chipped condition. Examine tappet-guide matching surfaces for scuffing or grooving.

When tappet fit in guide exceeds maximum tolerance shown in "Engine Specifications" by .001 in. or more, replace worn parts. If roller is loose, force out pin on arbor press, insert new parts and peen or stake pin ends.

Check roller end clearance. Replace all units exceeding tolerances listed in specifications.

Tappet guide screw (4) Push rod hydraulic unit (2) Push rod cover cork washer (2) Tappet guide

Tappet and roller assembly (2) Tappet guide gasket Figure following name of part indicates quantity necessary for one complete assembly.

Figure 3D-3. Inserting Tappets on Guide

Figure 3D-2. Tappet Assembly - Exploded View

Figure 3D-3. Inserting Tappets on Guide


Hydraulic units may be checked as follows:

Wash and air dry piston and cylinder. Blow out cylinder from bottom to make sure ball and seat are dry. Insert piston in cylinder. Hold in an upright position and press down piston, until spring touches cylinder, without covering hole in bottom of cylinder. Hold for count of 6 and release. If piston bounces back, unit is serviceable. If piston does not bounce back, cover hole in bottom of cylinder and repeat above process. If piston does not bounce back, unit is worn and must be replaced. If piston bounces back, ball is not seating, and unit should be replaced. Before replacing hydraulic units, check possibility of plugged or partially plugged screen under large cap screw located near rear tappet guide. Remove screen as described in "Disassembling Gearcase," and operate engine without screen and cork washers long enough to compare results.


Assemble tappets as follows:

Slip tappets (5) into guide (4) so flat surfaces on tappets are toward center of guide as shown in Fig. 3D-3. If flat surfaces with holes are not toward center of guide, engine oil will not feed across and one hydraulic unit cannot fill with oil. Assemble tappet guide gasket dry and insert tappet assembly in place on gearcase, holding tappets in place with thumb and forefinger as when unit was removed.

Assemble push rod cover cork washers, push rod hydraulic units and tappet guide screws.

Assemble remainder of push rod assembly in same order disassembled.

1. Oil screen cap

2. Cap gasket

3. Oil screen body

4. Oil screen

7. Generator fastening screw (2)

8. Gear cover

9. Gear cover gasket

10. Idler gear spacer

11. Intermediate gear spacer

12. Breather valve spacing washer

13. Cam gear

14. Cam gear spacing washer

15. Cam gear thrust washer

16. Breather valve and gear

17. Intermediate gear

18. Idler gear

19. Gear shaft nut

20. Pinion gear

21. Pinion gear key

22. Pinion gear spring

23. Gear shaft pinion spacer

24. Oil pump pinion shaft gear

25. Oil pump pinion shaft gear key

26. Breather screen

27. Breather separator

28. Oiler drive gear shaft spring ring

29. Oiler drive gear

30. Oiler drive gear key

31. Needle roller cam shaft bearing

32. Intermediate gear stud

33. Idler gear stud

34. Idler gear bushing

35. Intermediate gear bushing (2)

36. See item 35

37. Gearcase cover cam shaft bushing

38. Gearcase cover pinion gear bushing

Figure following name of part indicates quantity necessary for one complete assembly.

Figure 3D-4. Gearcase - Exploded View gearcase timing gears


The gearcase, located on the right side of the engine crankcase, contains a train of gears which transmit engine power to the cam shaft, crankcase breather, timer, oil pump and generator. The gearcase is lubricated with engine oil through the by-pass circulatory system and through the breather valve from engine crankcase.

All gear shafts run in bushings except the crankcase side of the cam shaft which operates in a needle roller bearing. The circuit breaker (timer) gear and intermediate gear turn on stationary shafts and are fitted with bronze bushings.


Before disassembling gearcase, it is advisable to remove push rods, tappets, push rod hydraulic units and tappet guides as described in "Disassembling Tappets."

Remove oil screen cap (1), gasket (2), screen body (3), screen (4), and two screen seals (5). Remove screen from screen housing by rotating screen until notch in screen lines up with key in housing.

Remove 12 gearcase cover screws (6) and two long generator fastening screws (7) and remove generator.

Remove two timer-to-motor bolts and slip timer assembly out top of gearcase.

Tap gearcase cover with wood or rawhide mallet to loosen and remove gearcase cover (8) and gearcase cover gasket (9).

Remove idler gear spacer (10) and circuit breaker drive and intermediate gear spacer (11). Make a mark on one of the spacers to insure its assembly to the same gear. The spacers look identical but one may be thicker than the other.

Remove breather valve spacing washer (12).

Remove cam gear (13), spacing washer (14), and thrust washer (15).

Remove breather gear (16), intermediate gear (17) and idler gear (18).

Remove pinion gear shaft nut (19) which has a left-hand thread. Use Gear Shaft Nut Socket Wrench, Part No. 94555-55. Pull pinion gear (20) using Pinion Gear Puller and Installer, Part No. 96830-51 as shown in Fig. 3D-5. Tool has lefthand threads.

Remove key (21). Slip off spring (22), gear shaft pinion spacer (23), oil pump pinion shaft gear (24) and key (25).

Slip breather screen (26) and separator (27) out of pocket in gearcase.

Remove oiler drive gear shaft spring ring (28), oiler drive gear (29) and oiler drive gear key (30).

If necessary, remove oil pump stud nuts and washers and remove oil pump from gearcase. See "Disassembling Oil Pump."


Wash and air-dry all parts. Wash inside of case. If crankcase is to be disassembled, wash parts after complete disassembly. If it is not to be repaired, be careful to get no grease solvent into crankcase when washing gearcase.

Inspect oil screen (4) carefully to make sure mesh is open. Holding screen to light is not an absolute check. It is possible for oil screen to be plugged or partially plugged with tiny lint-like fibers and still permit light to pass. Replace plugged or partially plugged screen. Probe oil screen hole in gearcase with a length of wire formed to a short hook to determine if there are any additional oil screen seal gaskets (5) in hole. More than the prescribed two will block off oil feed channel when screening unit is assembled.

Inspect breather screen (26). It must be clean and unobstructed.

Inspect cam gear and pinion gear bushings (37 and 38) in gearcase cover for pitting, scuffing and grooving. Determine amount of pinion and cam shaft wear in cover bushings. If it exceeds maximum tolerance shown in "Engine Specifications," Section 3A, by .001 in., install new bushings.

Inspect intermediate and idler gear fit on respective shaft. Examine bushings (34, 35 and 36) and stud shaft for pitting, grooving or scuffing. If amount of wear exceeds maximum tolerance shown in "Engine Specifications" by .001 in., replace bushings and/or stud shafts (32 and 33).

Attach dial indicator to gearcase cover mounting screw hole and determine amount of pinion shaft play in right main roller bearing. When tolerance in "Engine Specifications" is exceeded by .001 in., bearings should be replaced.

Inspect needle bearing (31) for wear, broken or gouged bearings. If end of cam shaft shows any appreciable wear (.003 in. or more), needle bearing is probably worn to a point where replacement of bearing and cam shaft are advisable.

Pinion shaft main roller bearing and cam shaft needle roller bearing may be replaced only when crankcase is disassembled (see "Disassembling Crankcase," Section 3E). Press needle roller bearing into crankcase from heavier end bearing the manufacturer's name only. Pressing from opposite end will crush roller race and bind rollers. Push new bearing into crankcase from gearcase side.

Figure 3D-5. Pulling Pinion Gear

Inspect gears for wear. Assemble pinion and cam gears to respective positions in gearcase. Mesh is considered ideal when no play between gears can be felt and cam gear can be moved back and forth along shaft axis without restriction. Omit cam gear end spacer in assembly for purposes of this check and attach cover with at least four cover screws.


Remove pinion shaft cover bushing as follows (Fig. 3D-6):

Use tip of Gear Shaft Bushing Remover, Part No. 96760-36, under hand pressure, to ream old pinion shaft bushing until hole has been enlarged enough to turn in smallest tap as shown in Fig. 3D-6. When first tap bottoms against shoulder, bushing may be pulled using puller nut and sleeve. If preferred, bushing may be drilled 5/8 in., tapped and pulled using above tool.

Install new pinion gear shaft bushing (38) in hole in cover as follows:

Position bushing in cover so oil hole in bushing is exactly in line with lubrication channel outlet in cover. Press in bushing on arbor press until top of bushing is flush with cast bushing boss on cover. Locate and center punch new dowel pin location 1/8 in. or more from original location. Drill No. 31 hole 3/16 in. deep. Press in bushing until it bottoms on shoulder in cover boss hole. Continue drilling dowel pin hole to depth of 9/32 in. from top of bushing. Drive in new dowel pin and carefully peen edges of hole to lock pin in place.

To replace cam shaft cover bushing, proceed as follows:

Use Gear Shaft Bushing Remover, Part No. 96760-36, to extract old bushing. Make a mark on outside of bushing boss to locate original dowel pinhole. Press in new bushing with arbor press until shoulder is against cover boss. Locate new dowel pin hole at least 1/8 in. from original hole, centerpunch and drill No. 31 hole exactly 9/32 in. deep. Drive in new dowel pin and peen bushing edges over dowel to secure it.

Drill lubrication oil hole through wall of bushing with 5/32 in. drill, using oil hole in bushing boss as a drill guide.

Pinion shaft and cam shaft bushings must be line reamed to remove burrs and irregularities from hole

Pinion shaft and cam shaft bushings must be line reamed to remove burrs and irregularities from hole

Figure 3D-6. Removing Pinion Shaft Cover Bushing 3D-6

Figure 3D-7. Line Reaming Cover Bushing and to insure perfect alignment. If crankcase is not disassembled, use any right crankcase side. Fasten cover in place with at least four screws.

To ream pinion shaft bushing, insert reamer pilot in right crankcase roller race. Insert 9/16 in. Pinion Shaft Cover Bushing Reamer, Part No. 94805-57, through pilot and push into cover bushing until it bottoms (see Fig. 3D-7), then give reamer one complete turn to size bushing. Rotate reamer the same direction (clockwise) during extraction.

To ream cam gear cover bushing, insert Cam Gear Shaft Bushing Reamer, Part No. 94802-36, through needle bearing in crankcase, into cover bushing. Turn reamer until it bottoms in gearcase cover.

Bushings in intermediate and idler gears may be pressed out on an arbor press using a suitable drift pin, and new bushings pressed in.


Before assembling gear train, determine amount of end play in breather gear as follows: Assemble breather gear and dry cover gasket to gearcase. Select spacer washer (use washer disassembled unless it is known to give incorrect spacing) and position on

1. Pinion gear

2. Cam gear

3. Breather gear

4. Circuit breaker drive gear

5. Intermediate gear (not marked)

6. Generator drive gear (not marked)

7. Oil pump drive gear (not marked);

secured on end of pump drive shaft with key and spring ring

Figure 3D-8. Timing Gears

Figure 3D-9. Installing Pinion Gear

end of breather gear. Place a steel straightedge across gearcase at spacer. With thickness gauge, measure distance between straightedge and spacer. Subtract .014 in. (thickness of compressed gasket) from this figure to determine gear end play. An end play tolerance of .005 to .008 in. is correct. If end play exceeds maximum, insert thicker spacer. Breather valve and gear spacer washers are available .115, .120 and .125 in. thick.

Establish proper cam gear end play as follows: Install thrust washer, spacing washer and cam gear. Position cover gasket and secure cover with at least four screws. Measure cam shaft end play between cam gear and cover bushing with thickness gauge through tappet guide hole in gearcase. End play should be from .001 to .005 in. If measurement is under or over tolerance, remove cover and replace spacing washer with one to give suitable clearance. Cam gear spacing washers are available .050, .055, .060, .065 and .070 in. thick.

Make final gearcase assembly including all parts in approximate reverse of disassembly order. Fig. 3D-9 shows use of Tool Part No. 96830-51 to install pinion gear. Breather, cam, pinion and intermediate gears contain timing marks which must be aligned or matched as shown in Fig. 3D-8. Rotate gear train and note if it revolves freely. A bind indicates gears are meshed too tightly. Make sure intermediate and idler gear spacers are assembled to their respective shafts.

Position new cover gasket and cover and secure with all cover screws. Pour about 1/4 pint of engine oil over gears to provide initial lubrication before securing cover.

Assemble remainder of gearcase, generator and circuit breaker in reverse of order removed.


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