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Adjust 4 stoke Valve Clearances
The valve clearances should be adjusted occasionally (I do it once per year for frequently used engines). Saito, as do most manufacturers, provide a small thickness measuring device with each engine. The Saito thickness gauge is 0.10 mm thick and can be used to determine if the valve clearances exceed the maximum recommended value; however I am unable to see how it is to be used to make a correct setting. It is best to use feeler gauges, or thickness gauges, obtainable from an auto parts store to set the clearances in the recommended range. The recommended range is 0.002 to 0.004 inches (or 0.03 to 0.10 mm) and I set the value about 0.002 - 0.003 inches. To adjust the valves: first remove the valve covers and then rotate the engine shaft until the valves are closed on the compression stroke. When the valves are closed you will be able to jiggle the tappet rocker arm up-down a little when you grasp it with your fingers. Next loosen the lock nut and turn the adjustment screw to get the proper gap. The 0.002 inch gauge should easily slide through the gap with no friction whatsoever. Thicker gauges such as 0.005 should not slide though the gap, or perhaps will go through the gap with some forcing. Tighten the lock nut and re-check the gap. Oil the rocker arm pivot and drip some oil down the push rod tubes, and then re-install the valve covers.
Note: Some purists, or mechanical nerds, will tell you that the above method to set the valve clearances using thickness or 'feeler' gauges is not the most accurate method. They argue (correctly) that use of a dial gauge is the better more precise method because after some engine wear the surfaces either side of the gap to be measured are not precisely flat. Therefore use of 'feeler' gauges results in a slightly larger gap than suggested by the thickness of the gauge. While this is strictly correct, I suggest the minimal difference is not significant, and use of a dial gauge is not something the average flyer is willing to fiddle with.
