I am having a problem with the High Speed Idle on my 11 HP Honda Snowblower. When running at Full speed with no load at all, the engine rpms are not constant. It is surging every second or two. Other than that the machine has plenty of power and runs very smooth when under load and throwing snow. I noticed there are 2 adjustment screws on the carburetor. There is a small straight slotted screw just above the bowl and another larger Phillips screw further up on the carb. Does anyone know if either of these screws are for the fast idle? The spark plug looks like new and is gapped set to .030 as per the manual. Other than that the machine looks like new and has only seen new clean gas each year. I purchased it new about 5 years ago. Any help will be greatly appreciated. I was ready to take this back to the dealer to get it fixed but after looking at the carb decided it may just be a simple adjustment. I have a 350 foot driveway and can't afford to have this machine go down on me.