Valve clearance check or tappet settings are often heard terms from mechanics; it is basically the adjustment of a cam follower (tappet), but before that let me explain you what is ‘a tappet’. It is the part that runs on the camshaft and is made to move vertically by the action of the rotating cam. In an overhead valve engine, this tappet is fitted low down in an engine block. From there, it drives a long thin push-rod, up to the top of the engine, above the cylinder head. Then there are the rockers; arranged on a rocker shaft beneath the rocker cover, reverses the direction of the valve movement to press the valves downwards to open them.
Here the cam lobe pushes the push rod which moves the tappet(the part above the valve return spring, attached to the rocker arm). If the valves are too tight the engine may experience rough running characteristics in either hot or cold or all the time. Too loose and they may produce a rattling sound which is quite unpleasing to the driver and is also likely to increase when you accelerate.
It is advised by experts to adjust tappet settings frequently whenever the cylinder head is removed and, get them checked every 3000 km as they stretch slowly and you would likely get tighter valves which results in burning of the valves (especially the exhaust valve) and then they start leaking hot gases when they are too tight. Frequent adjustment of tappets allow you to check a faulty valve and replace them or else you are expected to pay for heavy repairs.
The distance is set by using SHIMS (a thin piece of metal used to adjust the distance between two moving parts) of various thickness, they are inserted between the gaps and you are required to adjust the screw until it matches the thickness of the shim.
Too much mistakes in article and very vague discussion……..first of all tappet is not cam follower in all engines….its valve to rocker arm clearance in flat tappet like suzuki F8b F10a etc…….and tappet is generally old term before invent of hydraulic valve lashes…..now its simply “valve clearance” thats why we dont find term tappet in service manuals etc……..now for OHV engines these tappets are not in engine block, they are above valves like honda cg125 engine or chinese gensets…..or even toyota 3k,4k,7k……5k is another story having hydraulic lash with OHV…….now comes other engines…….they have no rocker arms, camshaft directly rolls over hydraulic lashes……their clearance is adjusted by shims aka “sikka” and they are not required to adjust by “screws”…….they are in suzuki g10 cultus engine……and nearly all new toyota engines……they are adjusted by availabe shims……clearance is measured before and then shims are placed to rectify it……hence please “at least” do a wikipedia search before writing…thank u.
Get them checked every 3000km? Why not every 50 yards? Are you posting from mid twenty century?
Whenever cylinder head is removed? Yes, we all get cylinder head removed every Saturday afternoons, or in holidays, twice a week.
Buahaha! was that some kind of joke? 😛