I highly recommend NOT checking the accelerator pump while the engine is running. If it backfires through the carb like he says it's doing he could fry his eyeballs. I learned the hard way when I was 17 not to look down the throat of a carb and hit the gas while it's running. Took 3-4 weeks for my eyebrows and hair to grow back. Lucky for me I wear glasses or I might be blind today because of it. You can check the accelerator pump just the same without the engine running.