John Deere B, grinding tappets

pmarkel

Member
The tappet heads are cupped on the rocker arm assembly of my 48' JD B, preventing accurate clearance adjustment with a feeler gauge. I found a "good, used" assembly on Ebay for cheap and bought it for a spare (as far as I know, they aren't making these parts anymore so good to have extra). I plan to have the purchased assembly ground and inspected for other signs of wear. Is there anything particular I should keep a look out for and what is the best way to have the tappet cups ground? I assume I can't just file them or run them on the side of a grinding wheel. All input appreciated.

Sincerely,

Peter Markel
 
You can adjust the tappet clearance to .020 without grinding the tappet heads. With each cylinder at
TDC on compression, loosen the jam nut and turn the adjusting screw "in" until a slight drag is felt
when the push rod is rotated. Then turn the adjusting screw "out" 1/3 turn and lock down the jam
nut. This will give you .020 clearance.
 
You can take them all apart and grind them on an attachment for a valve grinder machine if you can find one. Or you can leave assembled but removed from tractor and flipped over on workbench and use an angle grinder follow the original curve and retouch them up. Very quick and easy to do. doesn't usually take much to clean them up. At the wide gaps and slow RPM's they don't have to be perfect.
 
(quoted from post at 18:36:27 05/02/17) You can take them all apart and grind them on an attachment for a valve grinder machine if you can find one. Or you can leave assembled but removed from tractor and flipped over on workbench and use an angle grinder follow the original curve and retouch them up. Very quick and easy to do. doesn't usually take much to clean them up. At the wide gaps and slow RPM's they don't have to be perfect.
lease excuse this novice question but I haven't adjusted the valve lash on this tractor for a couple years. When you say "original curve" of the tappet surface, were the tappet heads not completely flat when new? The section on tappets in the JD service manuals just seems to indicate that the tappet surface should be made uniform via their dressing wheel attachment. Having never repaired tappets or seen them in any condition resembling new, I'm not real familiar with the specifics.

Thanks,

-Pete
 
Yes the face of the rocker arms is curved like this, ( and length wise to the rocker arm. You should easily see the unworn portion when removed from the tractor.
 

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