Will the scooter's valve be too tight to cause black smoke? Is it too loose?

If the valve of the scooter is adjusted too tightly, it will not close properly, especially if the gap of the exhaust valve is adjusted too small, which will make some unburned mixture enter the exhaust pipe and form black smoke. Tight adjustment of valve clearance will also lead to poor compression, which will lead to difficulties in starting a cold car, unstable idle speed, easy flameout, increased fuel consumption, decreased power, serious carbon deposition at the valve port, and wear of the valve rocker arm and camshaft.

If the valve is too loose, that is, the gap is too large, it will produce knocking sound. Excessive clearance will cause insufficient valve opening, which will affect the intake and exhaust volume and cause insufficient power. Valve clearance can only be adjusted to the specified value, not too large or too small, otherwise it will cause adverse consequences.