Timing Ignition By Piston Position

Check point gap (3) with breaker lever fibre block on highest point of cam. Gap should be .022". Adjust by loosening the two lock screws (2) and shifting adjustable contact plate. Measure gap with accurate thickness gauge before and after tightening lock screws.

Turn engine in direction in which it runs, until front piston is 7/16" (O.H.V. Engine), or 11, 32" (Side Valve Engine), before top dead center on compression stroke. With piston in this position, adjust circuit breaker so narrow cam (the one with mark) just starts to open points when breaker lever (8)—194G and earlier Models, or timing adjusting stud—1947 Models, is advanced fully.

An accurate check as to when points just start to open can be made with a test lamp. Use of such a not available, as in some cases a leak-free joint cannot he obtained with used gasket. Make sure tops of cylinders and cylinder head faces are clean. Apply a light coat of engine oil or grease to both sides of gaskets and install gaskets.

Turn engine so rear cylinder tappets are at their lowest position and install rear cylinder head, push rods and push rod covers in one operation. Be sure push rods register in tappet screw sockets at bottom end and rocker arm ball studs register in push rod sockets at upper end. It is recommended that the three cork washers (6), (11) and (13), Illus. 15, for each push rod cover be renewed.

Install cylinder head bolts with flat washers under head of each bolt. Bolts must be tightened evenly to attain a tight joint. First turn bolts just snug; then tighten each of them Va or V* turn at a time until all are securely tightened. Use Harley-Davidson special wrench, Part No. 12650-29. Follow same procedure for installing front cylinder head.

In connection with top overhaul only (which does not require removing muffler), insert exhaust pipes in cylinder heads as heads are lowered onto cylinders.

Remove top center crankcase stud nut (right side) and drive the stud in flush with crankcase.

Check intake manifold packing bushings to see that they are in good condition. Assemble nuts and bushings to manifold after applying a light coat of oil or grease so bushings will freely adjust themselves to manifold and cylinder head nipples as nuts are tightened. Align the hole in carburetor support bracket with top center crankcase stud, then drive stud end through hole in bracket and install stud nut and tighten securely. Turn nuts onto cylinder head nipples and tighten securely with Harley-Davidson special wrench. Part No. 12002-40. Unless manifold packing bushings are in good condition and manifold nuts securely tightened there are likely to be air leaks around manifold-cylinder head joints. With this condition it will not be possible to get a satisfactory low speed carburetor adjustment.

After manifold is tight, loosen cylinder base nuts slightly to allow final shifting and lining up of cylinders and manifold, then tighten base nuts securely, using Harley-Davidson special wrench, Part No. 12050-30.

Cylinder head bracket cannot be installed until after engine is in chassis.

Installing Cylinder Heads (Side Valve Engine)

It is recommended that new cylinder head gaskets be used each time heads are installed. This assures leak-free joints. Old gaskets should be reused only in an emergency when new gaskets are not available, as in some cases a leak-free joint cannot be obtained with used gasket. Apply a light coat of engine oil or grease to both sides of gaskets. Make sure tops of cylinders are clean and install gaskets. Jf engine has aluminum heads, place heads on cylinders and install convex washers (large surface against head) and head bolts. Attach cylinder head bracket (mounting lug to left side of engine) with a convex washer between bracket and cylinder head, and a flat washer under head of each bolt, above bracket.

If engine has iron heads, place heads on cylinders and install flat washers and head bolts. Two flat washers are thicker and larger than the others and are to be installed above cylinder head bracket. Attach cylinder head bracket (mounting lug to left side of engine) with smaller flat washers between bracket and cylinder head, and a larger flat washer under head of each bolt, above bracket.

Head bolts must be tightened evenly to attain a tight joint. First turn bolts down just snug; then tighten each of them Va to V* turn at a time until all are securely tightened. Use Harley-Davidson special wrench, Part No. 12047-30H.

Adjusting Valve Tappets

Valve tappets must be checked and adjusted each time cylinders—Side Valve Engine, or, cylinders or cylinder heads—O.H.V. Engine, are removed and installed. See "Adjusting Valve Tappets," Pages 22 and 23.

Installing Engine in Chassis

In connection with top overhaul only, engine is already in chassis and completing assembly is a matter of reversing the procedure followed in disassembly as outlined under "Disassembling Engine for Top Overhaul Only," (O.H.V. Engine), Page 37; (Side Valve Engine), Page 40.

In the case of a complete engine to be installed in chassis, reverse procedure followed in removing engine from chassis as outlined under "Removing Assembled Engine From Chassis for Complete Overhaul," Page 41.

O.H.V Engine—Attach cylinder head bracket and secure to cylinder heads with flat washers, lock washers and nuts; install required number of shim washers to fill space between cylinder head bracket and frame lug, insert bolt through these fittings, and install and securely tighten nut.

Side Valve Engine—Pay close attention to the following: Install required number of shim washers to fill space between cylinder head bracket and frame lug, insert bolt through these fittings and install and securely tighten nut; bear in mind that clamp for front spark plug cable is also attached with this bolt.

All Models—Be sure throttle and spark control clamps are tightened securely and check very closely to see that throttle opens and closes fully with grip movement and that spark advances fully with grip in inward position. Check clutch, gear shifter and brake controls for correct adjustment. Make close final inspection to be sure all nuts, bolts, screws, etc., are tight.

Emergency Piston and Ring Service

Need of replacement of rings, or possibly pistons and rings, is indicated by loss of normal compression, overheating, loss of power, abnormal oil consumption, excessive exhaust smoke and piston slap or knock.

As explained under "Refinishing Cylinders Oversize and Fitting New Pistons," Page 45, when pistons develop excessive clearance and slap due to wear or damage and cylinders are found worn more than .002", it is recommended regular practice to smooth and true up cylinder bore by honing, or boring and honing, to the next regular oversize piston step.

However, piston slap alone, due to wear and excessive cylinder-piston clearance, does not necessarily mean otherwise very poor and undependable performance. A good compression seal is the re-guirement of prime importance for good performance. Therefore, in rendering emergency service, when oversize pistons are not at hand, the main things to be considered are whether or not cylinders are deeply scored and piston ring grooves badly worn sideways.

Even though cylinders and pistons may be worn to the extent of pronounced piston slap, if cylinders are in smooth condition so a new and reasonably good compression seal can be affected by fitting new rings, or new pistons and rings, if ring grooves are badly worn, engine will be good for a further period of dependable performance.

See "Checking Connecting Rod Lower Bearing for Excessive Wear and Looseness," Page 40.

Piston and Pin

(Removing and Installing)

Piston pin, properly fitted, is a light hand press fit in piston and has .001" clearance in connecting rod upper bearing. The pin is secured in piston by means of a spring lock ring at each end of pin. Lock rings fit into grooves in pin and grip pin with considerable tension.

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Responses

  • Patrick
    How to lock knucklehead timing?
    2 years ago
  • sandy
    How to set ignition with piston position?
    2 years ago

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