I have a '98 Great Dane Surfer with a 18 hp Briggs Vanguard OHV recoil start V-twin engine. All of a sudden it started running a little crappy, but never kills. It started blowing a good amount of black smoke and it lost a lot of power. I changed the plugs because they were both as black as could be. This didn't seem to help though. My next idea is to check compression. My question is: what should the range of compression be for this engine? Is there anything else I am missing here? I have a funny feeling that I lost a cylinder but I won't know until I do the compression check. Thanks for any info or help you can give me on this.