B Insert a small-hole gauge into the

valve guide and expand it so there's a

slight drag when it's pulled out

C Measure the small-hole gauge with a micrometer

Engine, clutch and transmission 2*19

Check the valve face (A), stem (B)

And collet grove (C) for signs of wear and

Damage

A Measure the free length of the valve springs

B Check the valve springs for squareness

to obtain the valve stem-to-guide clearance. If the stem-to-guide clearance is greater than listed in this Chapter's Specifications, the guides and valves will have to be renewed. If the valve stem or guide is worn beyond its limit, or if the guide is worn unevenly, it must be renewed.

16 Carefully inspect each valve face for cracks, pits and burned spots. Check the valve stem and the collet groove area for scuffing and cracks (see illustration).Rotate the valve and check for any obvious indication that it is bent. Check the end of the stem for pitting and excessive wear. The presence of any of the above conditions indicates the need for valve servicing.

17Check the end of each valve spring for wear and pitting. Measure the spring free length and compare it to that listed in the specifications (see illustration).If any spring is shorter than specified it must be renewed. Also place the spring upright on a flat surface and check it for bend by placing a ruler against it (see illustration).If the bend in any spring is excessive, it must be renewed.

18 Check the spring retainers and collets for obvious wear and cracks. Any questionable parts should not be reused, as extensive damage will occur in the event of failure during engine operation.

19 If the inspection indicates that no overhaul work is required, the valve components can be reinstalled in the head.

Reassembly

20Unless a valve service has been performed, before installing the valves in the head they should be ground in (lapped) to ensure a positive seal between the valves and seats. This procedure requires coarse and fine valve grinding compound and a valve grinding tool. If a grinding tool is not available, a piece of rubber or plastic hose can be slipped over the valve stem (after the valve has been installed in the guide) and used to turn the valve.

21Apply a small amount of coarse grinding compound to the valve face, then slip the valve into the guide (see illustration). Note:Make sure each valve is installed

in its correct guide and be careful not to get any grinding compound on the valve stem.

22Attach the grinding tool (or hose) to the
valve and rotate the tool between the palms of
your hands. Use a back-and-forth motion (as
though rubbing your hands together) rather
than a continuous circular motion (ie so that
the valve rotates alternately clockwise and
anti-clockwise rather than in one direction
only) (see illustration).Lift the valve off the
seat and turn it at regular intervals to
distribute the grinding compound properly.
Continue the grinding procedure until the
valve face and seat contact area is of uniform
width and unbroken around the entire

circumference of the valve face and seat (see illustrations).

23Carefully remove the valve from the guide and wipe off all traces of grinding compound. Use solvent to clean the valve and wipe the seat area thoroughly with a solvent soaked cloth.

24 Repeat the procedure with fine valve grinding compound, then repeat the entire procedure for the remaining valves.

25 Lay the spring seat for the first valve in place in the cylinder head, with its narrower shouldered side up so that it fits into the base of the spring, then install a new valve stem

Date: 2016-01-14; view: 995