I was taught back in the early 1960 when all gasoline had lead in it to use a spray bottle full of water only and warm the motor up to operating temps and then spray enough water down the carb slowly at or above 3000 RPM to start to slow the RPM down a little, 200 to 400 RPM, for as long as the water bottle had water in it, probably around 8 ounces That worked really good on cleaning out the carbon