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Setting Valves On Yanmar Tractor
There are many schools of thought on the best way to set the valves on a 4 stroke engine. Some books  recommend that you align timing marks & check for top dead center of a certain cylinder. I have had the opportunity to work with some of the best CAT & DEERE mechanics around and the method below is the way they have all used. It is simple, it works on all engines, and you don't need a manual to find timing marks or which cylinder should be TDC.
How It Works Use a socket or special tool to turn over the engine. Watch the valves move as you turn the engine over. You will see the valves slowly go up, then stop, then start going down. You want to check the gap between the valve stem & the rocker arm when the valve is exactly in the middle of that 'stopped" position. This is when the valve is completely closed & the push rod will be loose. Pick a valve- we usually start at the back but it does not matter. Loosen the locknut & adjust the bolt until you can feel a drag on the feeler gauge when you slide it in or out. If it is too hard to pull it out, you are just compressing the spring & need to loosen the bolt a little. If you can't feel any drag, tighten it up a little. You just want a little drag on the feeler gauge. All Yanmars set at 0.006" to 0.008" intake & exhaust so use a feeler gauge of that size. Tighten the locknut & re-check. Move to the next valve. Do the same thing until you have set all of the valves. Wasn't that easy?
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