Qian Jianglong 19c exhaust pipe shooting problem, please ask the great god for advice.

It is normal for the engine to get hot. The engine is a high temperature component. The fire will be very hot inside and outside. It will be very hot after starting or running for a few minutes. This is normal. As long as the oil is normal and the driving operation is fine, don't worry.

When driving at high speed, the throttle valve will suddenly close, and the air intake will immediately decrease, resulting in the instantaneous thickening of the mixture and the explosion of the exhaust pipe. This situation will also occur in other cars, which is basically a normal phenomenon, and some cars will also stall. Some carburetors have special valves to alleviate this situation. Of course, this has something to do with the performance or debugging matching of the carburetor itself, but it is not a big problem or failure, which will not affect the use and will not cause any damage. Just pay attention to the driving method. There are many reasons that affect the color of spark plugs. As long as the spark plug doesn't break down frequently and there are no other abnormalities, you don't have to pay too much attention to its color. Judging from the color of the spark plug you described, there should be no problem.