If it is assumed that the required pressure is not being created in the cylinder, it can be checked using a compression gauge. To check, unscrew the spark plugs, insert a compression tester into the corresponding hole in the spark plug and turn on the starter. The instrument indicator gives the compression value. This detects leaky valves, pistons or piston rings. If the engine is still fairly new, the compression value should lie within the values from Specifications.
The specified wear limits must not be reduced. If the compression is low, you should consider installing another engine or rebuilding it. It is also very important whether one cylinder has insufficient compression or all. If, for example, the compression in one cylinder differs by 1.0 bar, it may be that the cylinder valves are stuck and only the cylinder head, i.e. the valves, needs to be repaired. It may also be that the piston rings are stuck, and the gases along the piston go into the crankcase. If compression improves when a small amount of oil is added to the cylinders, this is a sign of worn piston rings. With a uniform loss of compression, in most cases the cylinders are worn out.