Engine servicing

Clatters in the crank mechanism are a good signal of abnormal operation. They can be the result of the following faults:

1. The wear of the crankshaft bearings, the piston pins and their bushings. The worn parts are replaced by new ones.

2. An increase of the cylinder diameter. In this case new pistons must be set.

3. The piston wear. To repair one must replace them by new ones.

Compression reduction is the result of the following faults in the crank mechanism:

1. The wear of the rings, the cylinder walls or the bushes. The engine should be repaired.

2. Scratches on the operating surface of the cylinders and the bushes. During maintenance the scratches should be smoothed.

3. The piston rings sticking in the piston slots. Pour 15 g of a mixture made of kerosene and alcohol (in a proportion 2:1) into the cylinders and leave for a night. In the morning start the engine to remove the dissolved resins.

4. The cylinder head fitting is not tight, or the gasket under it is damaged. Replace the damaged gasket with a new one.

To replace the gasket do the following:

a) remove all the devices from the engine head, let the water out of the cooling system;

b) unscrew the nuts and the bolts, fastening the head;

c) remove the head and the gasket;

d) cover the new gasket with oil before setting it;

e) screw the bolts.

If there is no compression at all do the following:

a) unscrew all the plugs except the first cylinder plug;

b) using the starter lever, rotate the crankshaft until the compression stroke is completed;

c) screw the plugs according to the engine operation order and rotate the crankshaft again.

Some faults can be detected in gas-distributive mechanism.

1. The valves do not close tightly because of:

a) snuff or the cavities on the operating surfaces;

b) damage of winding of the valve head;

c) break of the valve spring;

d) valve sag.

All these faults cause misfiring and compression reduction. It is necessary to repair the engine or to adjust it.

2. The valves do not open completely because of the clearance in the valve mechanism. That results in a reduction in engine power.

The adjustment of the valve clearances can be performed only by highly qualified personnel.