When do you need to change spark plugs? Well, that depends. Generally in powersports, there really is no set timeframe in which the plug must be changed. Different factors will call for different intervals. For example, do you use only the cheapest fuel? Have you been unsuccesfully trying to start the unit for awhile? The excess starting attempts can foul the plug as well. Is your idle screw set too fast. A very fast idle may also damage a spark plug. Water in the fuel can cause a spark plug to foul, or misfire. Have you noticed a loss of power at higher speeds, or feel hesitation while acclerating? A spark plug is a quick, inexpensive thing to change to try to correct the problem.
The process shown in this video is universal in China made powersports. Whether you have an ATV, scooter, dirt bike or motorcycle, you will change the plug in the same manner. In some scooters, the seat box may need to be taken out to access the plug.
While many China made powersports come with an NGK plug in them, they can be cross-referenced to quite a few different brands. You should follow the gap specifications in your owner's manual.
On atvs, it is a good idea to spray a little silicon or grease over the spark plug boot if you will be in alot of water. This can prevent the splashing water from fouling the plug.