Wei Chai engine, exhaust pipe injection, what is the reason?

Hello, the exhaust pipe of Wei Chai 336 engine is sprayed with oil because there is too much carbon in the throttle. Because the exhaust pipe is connected with the throttle valve, too much carbon deposit in the throttle valve will cause oil circuit blockage, so fuel can be injected from the exhaust pipe. Cleaning the throttle valve can eliminate this problem. The specific operation steps of cleaning the throttle valve are as follows: 1. First remove the air filter. 2. Spray the special throttle cleaner into the throttle. 3. Clean the carbon brush inside the throttle with a long rod brush. 4. The throttle will be cleaned. 5. Replace the air filter and complete the operation.