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This is because the valve plate was over-ground during maintenance and the grinding amount was too much, so the pressure between the valve plate and the cylinder plane is insufficient. At low throttle, the oil pressure is small, and it is not easy to leak between planes; at high throttle, the oil pressure increases, and overflow occurs between planes, causing the track to be unable to move at high throttle. The remedy is to add a gasket to the spring. If it is a butterfly spring, you can add an extra butterfly spring.

Reasons from the piston group
1. The piston ring gap is too small. If the opening gap, side gap or back gap of the piston ring is too small, the piston ring will be stuck due to heat expansion when the engine is working, and it will be pressed tightly against the cylinder wall, or the piston ring will be broken, which can easily pull out grooves on the cylinder wall.
2. The piston pin is out. Because the piston pin retaining ring is not installed or falls off or breaks, the piston pin will be out during movement, which can easily damage the inner wall of the cylinder and cause the cylinder to blow into the crankcase.
3. The piston cylinder gap is too small or too large. If the piston material is poor, the manufacturing size error is too large, or the piston is deformed after the piston pin is assembled, the matching gap between the piston and the cylinder is too small, and the piston is stuck after heat expansion, which will then damage the cylinder wall.
4. The piston ring is seriously carbonized. Excessive carbon deposits cause the piston ring to stick or bite in the ring groove. At the same time, carbon deposits are a hard abrasive that will grind into longitudinal grooves on the cylinder wall.
5. The piston is seriously off-cylinder. Due to the bending and twisting of the connecting rod, the parallelism and coaxiality deviations of the connecting rod journal, main journal, and piston pin seat are too large, causing the piston to be significantly off-cylinder, which will accelerate the wear of the piston ring, piston and cylinder wall and destroy the formation of the oil film.

Reasons for cylinder sleeves
1. The roundness and cylindricality tolerances of the cylinder sleeves exceed the allowable range, which greatly reduces the sealing of the piston and cylinder sleeves. The high-temperature gas in the cylinder flows down, destroying the oil film between the piston and the cylinder wall, and then causing cylinder pulling.
2. The cylinder sleeve is deformed during the assembly process. For example: the protrusion of the upper end surface of the cylinder sleeve is too large, and the cylinder sleeve is deformed after the cylinder head is installed; the cylinder sleeve water blocking ring is too thick, and the cylinder sleeve is deformed after being pressed into the body, which can easily cause cylinder pulling.

Reasons for use:
1. Whether the size of the cylinder sleeve used during assembly does not match the cylinder body and piston.
2. The air filter is not sealed, which makes the filtering effect worse. Dust, sand and other impurities in the air are sucked into the cylinder, forming abrasive wear. Tests show that if a few grams of dust are sucked in every day, the wear of the cylinder liner will increase by more than 10 times.

Possible low hydraulic oil level, clogged filter, internal wear, or hydraulic line leakage. Solution: Check oil level and refill, clean or replace filter, inspect and repair leaks, check and replace worn parts.

When the engine replaces new piston rings, pistons or cylinder liners, due to the initial poor running-in, it is easy for the engine oil to enter the combustion chamber and burn, producing blue smoke. This phenomenon can generally be gradually eliminated after running for 8-10 hours.

(1) The oil level in the oil pan is too high.

(2) The engine oil in the air filter leaks into the combustion chamber from the intake pipe and burns.

(3) The piston ring is bonded to the piston ring groove by carbon deposits, causing the engine oil to leak into the cylinder and burn.

(4) The piston ring is excessively worn, or when several piston rings are installed, the opening gap has been matched.

(5) The matching clearance between the piston and the cylinder liner is too large.

(6) The piston ring is not elastic enough.