Illus 35 Reaming Valve Guides

Install new valve guides by inverting cylinder and pressing or driving guides into guide holes until shoulder on guide is tight against cylinder. New valve guides are reamed to correct size. However, when guides are pressed into cylinders they may close up slightly; also the ends may be burred. Therefore, after new guides are in place, they should be sized and cleaned up with Harley-Davidson special reamer, Part No. 11894-30. See Illus. 35.

It is of prime importance that valve guides fit tightly in cylinders. If they don't, valves may not seat properly. If original guide or new standard guide is not a tight press fit, an oversize guide must be installed. Oversize guides can be obtained .001" and .002" oversize.

After installing valve guides, valve seats must be refaced to true them with the guides. See "Valve Seats," Page 47.


Before refacing valves, remove carbon from valve head and stem, using a knife and wire wheel—never


a file or other hardened tool that will scratch or nick valve. Polish valve stem with very fine emery cloth or steel wool. Check the valve stem for excessive wear; standard valve stem diameter is:

OJi.V. Engine: .374" to .375"; Side Valve Engine: .370" to .371". If valve is warped, this will be indicated when face is reground.

AU Models: Valve face angle is 45° for both intake and exhaust valves, and valve refacing grinder must be adjusted exactly to this angle. It is important not to remove any more metal than is necessary to clean up and true valve face. If grinding leaves the edge of valve very thin or sharp, install a new valve. A valve in this condition does not seat normally, will burn easily and may cause pre-ignition. There is also danger of cracking.

If end of valve stem shows uneven wear, true end of stem on a valve refacing grinder equipped with suitable attachment.

Intake and exhaust valves are made of different materials and must not be interchanged. Intake valves are marked "IN" on head; exhaust valves are marked "EX."

Valve Seats

Valve seats, like valves, are subject to wear, pitting and burning and should be refaced each time valves are refaced. Be careful that no more metal is removed than absolutely necessary to completely clean up and true valve seats.

O.H.V. Engine: Has valve seat inserts so hard that a seat cutter will not work—they must be refaced with grinder. Inserts should be checked for leakage and looseness in cylinder heads, and any found defective must be replaced. A leaky insert may cause overheating to the extent that piston may be seriously damaged.

Side Valve Engine: Seats can be refaced with either cutter or grinder, however, a seat refaced with cutter will not be as smooth as when refaced with grinder and a greater amount of lapping will be necessary to attain a perfect seat.

As valves and seats are refaced from time to time, valve seats widen and valves seat in lower position when fully closed. Also, passage around valve when fully open would be somewhat restricted. O.H.V. Engine: To correct this condition, will require replacing valve seat insert. Side Valve Engine: To correct this condition, additional clearance will need to be cut above seat so top edges of angular valve face and seat match exactly. Use Harley-Davidson special clearance cutter. Part No. 11890-47 (see Illus. 37 and Illus. 61).

When a valve guide is removed for any reason and replaced or a new guide installed, it is not likely to be concentric with valve seat. If a valve guide is not concentric or true with seat, leakage and burning of valve may result, or valve may break due to cocked seating and deflection of valve stem. Therefore it is especially important after installing new guides that seats be carefully refaced to make them concentric with guides and assure perfect alignment and matching of valve face and valve seat. See "Valve Guides (O.H.V. Engine)," or "Valve Guides (Side Valve Engine)," Page 46.

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