I have an older style carb Briggs 3hp. The type of carb with the pullout choke. The motor ran alright at times and would just idle at other times. I put on a new gasket where the carb mounts to the block. Ran it around and seemed the same with good and bad running. Cleaned and adjusted the only adjusting screw I could find on the carb, I think it was the high speed jet. Removed all the fuel yesterday from the tank and got some rust on a paper towel. Put new fuel in it and runs pretty well but still revs up to full speed and then bogs and just idles, let off the throttle and it give it throttle again and it takes off. I did this 3 times in about 200 feet. It is mounted to my Pack Mule so I can not get far fast. Any suggestions would be great.