Model A valve adjustment

Could somebody please explain the proper procedure for valve adjustment on a 1946 A?

The John Deere service manual says...Remove the spark plugs, bring the left side piston to top dead center. Adjust those two valves, then rotate the flywheel till the right side is at TDC, and adjust those two.
The book says they should be .020 hot, so I adjust mine to .022, or .023 cold. I'd sooner have them a tad loose than too tight.

Hope this helps you.

Popper is dead on. Here's the long version.

Devise, if you haven't already, a tool for turning the flywheel. A pipe with slots that fits over the pin in the center with a "T" so you can stick a bar in it is good. Some small crowbars can be jammed in and used to muscle it around. Be sure ignition/starter is off, removing the ground cable is best. On a magneto, use a jumper wire to ground the kill post if there's no switch. Remove both plugs and ground the ends of plug wires with jumpers. Be SURE that ignition/starter is DEAD. Take off the valve cover, disconnecting anything you have to along the way. Try to save the cork gasket in case you have to make a new one. Deere has them, but they are pricey. You should be able to get the valve cover completely out, or otherwise move it out of the way.

Turn the flywheel in direction of rotation (top forward). When #1 (left cylinder) is coming up on compression stroke, blowing air out past your thumb (or a friend's thumb, if he/she doesn't owe you any money) over the spark plug hole, stop. Bend a piece of wire and work it into the spark plug hole so the end rests on the top of the piston. Slowly rotate the flywheel until the movement of the wire "pauses". That's top dead center on #1. Both the intake and exhaust should be closed. At this point wiggle the rocker arms and be sure both are "loose". Using a bright light examine the surfaces where the pushrods and valves contact the rocker arms/adjusters--especially the valve/rocker arm contact point.

The best way to set the valve clearances is with feeler gauge. Some feeler is made with an angle to facilitate setting valves, but any will do--if you can use them. However, if the rocker arm is pitted where the valve contacts it, feeler will not work. If it's not too bad, you can remove the arm and dress the affected area with garnet cloth or similar substance. If they are badly pitted it may take a machine shop to build up and grind down the affected area. But there is a work-around. . .


If the rocker arm surfaces are good, loosen the locking nut on the adjuster and turn the adjuster until the pushrod will not rotate with thumb and index finger pressure. That's your "0" point. Now, the book sez the adjustment is .020" between the rocker arm and valve stem with the engine HOT. Set the valves cold to .022-.023. The feeler should slide out from between the rocker arm and valve stem with a slight but definite drag. If the rocker arm surfaces are NOT good, all is not lost (maybe). Zero the clearance and then turn out the adjuster 1/2 turn. Do both valves on #1, remembering to reset the locking nuts. Then turn the flywheel with your wire in #2 until it's on top dead center. Remember that #2 comes up on compression right after #1. Then set those valves with feeler or "turn of the wrench".

If you've used feeler to set the valves, you can start it up and get it hot, then check with .020 feeler. Better they be a little loose than too tight. If you're a perfectionist check them with the engine running. Remember that the oiler oils only the exhaust valves and the intakes are oiled by the splatter and fumes in the valve cover. Since you'll be running it with the cover off, a drop of oil on the intake stems doesn't hurt. Then you're feeling for the drag when the valve is closed vs the feeler being locked between the stem and rocker when valve is open. If you're not sure about a setting, turn the flywheel all the way until the cylinder comes up on compression-don't back it up and bring it up again. That's a pet thing of mine to be sure all the slop in the gears is taken up and it's exactly like it will be when its running. I once got to set the valves on a running R-985 radial airplane engine. That propeller whipping around next to you sure bothers the concentration, but it do keep the bugs away.

Good luck, the A is a mighty fine tractor.

Thank you for the long version. I am a one finger typist, and took the shortcut.
Dale

A real shortcut is to turn flywheel till left hand impulse mark points towards the lower governor cover bolt. If your on the right stroke all the tappets should be loose and
you can set all the valves at the same time without spinning it over again. We do it all the time that way on the pullers and you set them at the same spot each time so
you can tell if something is going on.

Thanks for the replies, will try it as soon as I get a chance