Replacing Valve Seats

After installing valve guides, valve seats must be refaced to true them with guides.

If valves have been reseated several times, valve seats may have become too wide and/or valve may be seating itself too deeply in head. When valve seat becomes wider than 1/16 in. (see Fig. 3B-3) valve seat relief must be counterbored or ground to reduce seat to 1/16 in. Counterbore dimensions are shown. Tools for this purpose are available commercially. To determine if valve is seating itself too deeply in head, measure distance from shoulder of valve guide to end of valve stem. See dimension in Fig. 3B-3. When valve stem extends through guidé excess of maximum shown valve seat inserts must be replaced.

A special gage is available under Part No. 96490-59A which is used to measure this dimension. The tool consists of gage valves and gage which is placed over the valve stem as shown. If top end of gage valve stem is between steps on gage, the valve seat location is satisfactory.

1966 and later inserts are pressed-in and cylinder heads may be returned to the factory for replacement with new inserts.

1965 and earlier cylinder heads, having cast-in inserts," may be returned to factory through authorized Harley-Davidson dealer for valve seat insert replacement. Heads are bored out to remove old seats, and new seats are pressed into place.

5/32 in. oversize service valve, Part No. 18082-60, is available for replacement of standard size, 1965 and earlier, intake and exhaust valves which are seating too deeply. A new valve seat must be cut in the old valve seat insert with boring or grinding tools according to instructions which come with service valve.

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