Adjustment of motorcycle valve clearance

First of all, in a working cycle of a four-stroke engine, the crankshaft rotates 720 degrees (twice), the piston goes back and forth twice, and the intake valve and exhaust valve open and close once.

That is to say, in a working cycle, the piston is at the top dead center twice, that is, the "T" coincides with the marking point twice, once for exhaust top dead center and once for compression top dead center. However, adjusting the valve clearance should be carried out at the compression top dead center (so the resistance is large at this time). How to judge whether to compress top dead center? It depends on the drive of the valve. When t is aligned with the mark, turn the rotor slightly to the left and right. At this time, both valves will not move, that is, the top dead center will be compressed. At this time, the valve clearance can be adjusted. On the other hand, it is the exhaust top dead center, that is, 180 degrees has a top dead center, and it cannot be adjusted when t is seen.

If you drive a little too much while looking for T, you can back up. The information you read may be scooters, and some scooters have "anti-reverse" devices. If it is reversed, the exhaust valve will be opened to decompress, laying the foundation for the next start (parking). At this time, the adjustment valve of scooter will be inaccurate.

The "f" of the rotor (magneto) represents the position of "ignition advance angle", which is generally about 12 degrees.

For your reference.